Data block format for software carrier and player therefor

ABSTRACT

An optical disk format for representing several synchronized signals, e.g., multiple versions of motion pictures and multiple soundtracks. All signals are represented digitally, and the bits are arranged in data blocks. Each data block may contain a variable number of bits for each signal, ranging from none to many (relative to the other signals). This allows each signal to be represented by a variable rate bit stream, without one signal necessarily constraining another as far as bit representation is concerned. Multiple buffers are provided to insure that there are a sufficient number of bits available for each signal as required for immediate needs. When any buffer is full, reading of the data blocks stops temporarily so that no bits are lost.

This invention relates to the play of software (e.g., motion picture)carriers, and more particularly to a data block format for such carriersand players therefor that allows efficient use of the bit capacity ofthe carrier so that numerous signals may be represented on the samecarrier.

BACKGROUND OF THE INVENTION

The most widespread medium for distributing motion pictures is thevideocassette. However, digitally encoded optical disks are in theoryfar superior for the distribution of motions pictures and other forms ofpresentation. Especially advantageous is the use of "compressed video,"by which it is possible to digitally encode a motion picture on a diskno larger that the present-day audio CD. Information storage on a higherdensity optical disk could allow a single disk to contain multipleversions (e.g., R-rated and PG-rated) of the same motion picture,multiple soundtracks in different languages, and data for other relatedor even unrelated signals.

Because of the different television industry standards used throughoutthe world, there are an equal number of videocassette standards. An NTSCvideotape sold in the United States, for example, will not play on mostvideocassette players to be found in England. In order for a softwarepublisher not to have to produce optical disks in as many differentformats as are presently required for videocassettes, it would be farpreferable for the data stored on an optical disk to be converted to aparticular standard by the player. That way, the same disk could be soldanywhere in the world. Because of the advantages offered by the storageof digital data on optical disks, it is possible to achieve thisflexibility along with the storage of so many different signals.

Despite the fact that optical disks afford tremendous bit densities,there are nevertheless limits to how much information (data) can bestored on an optical disk. Especially if multiple versions of a motionpicture, multiple soundtracks, and other kinds of signals are to bereproduced from the disk, care must be taken in how the data isorganized on the disk. Prior art approaches to disk data organizationhave been ill conceived. Considerable work has been done on developingcompressed video standards, especially the MPEG1 and MPEG2 standards,and one would have thought that the full bit savings offered by thesestandards would have made their way to optical disks. But that is notthe case. The approach being voiced by developers of optical diskproducts is one which establishes an average bit rate for a motionpicture, based on the compression afforded by the new standards, and useof that bit rate to represent the entire motion picture. This is not tosay that every represented frame requires the same number of bits.Clearly, an impetus for video compression is the fact that differentframes may be represented by different numbers of bits; relatively fewbits are required in going from one frame to the next which ispractically the same, while numerous bits are required to represent thefirst frame of a new scene. Nevertheless, system designers envisage thatthe number of bits per unit of time will be constant for the entireduration of a motion picture. Standard buffering techniques arecontemplated for storing a sufficient number of bits to represent asuccession of frames, with just those bits required for each frame beingaccessed at the frame rate. The basic shortcoming of this approach isthat it assumes that the same average bit rate is applicable to anentire 2-hour movie, when that may not be the case at all. For example,a car-chase scene that lasts for 15 minutes may require a very high bitrate, while other scenes in the same motion picture may require a verylow bit rate over an extended period of time. To apply a single averageto the entire motion picture results in the needless storage of bits forslow-changing scenes, and an insufficient number of bits to representfast-changing scenes.

What further complicates matters is that even if a variable bit rate isemployed, a rate which changes to reflect how much video informationmust be represented (as opposed to limiting the amount of informationthat can be represented with a fixed bit rate), the other signals storedon the disk may similarly be represented with maximum efficiency byemploying variable bit rates, but bit rates which vary differently fromthat required for the video. For example, a fast-changing scene with nosound requires a high video bit rate but a low soundtrack bit rate. Tomaximize the amount of information which can be stored on a disk, it isnot only necessary to employ a variable bit rate, but to employ variablebit rates for the different signals to be represented, with the severalbit rates changing in accordance with the needs of the respectivesignals that they represent rather than being keyed to each other.

It is a general object of our invention to provide a data storage formatfor a software carrier that permits efficient use of the bit capacity ofthe carrier.

It must be understood that the principles of the present invention arenot limited to any particular types of carriers or any particular kindsof software, although there is no question that the invention hasparticular application to optical disks. Nevertheless, it is to beunderstood that the invention is not limited to a particular medium (forexample, it is applicable to tape carriers and all digital storagemedia), nor is it limited to just the distribution of motion pictures.For example, in an extreme case, the invention is applicable to thedistribution of a library of still pictures, in which there is no"motion" at all. The term "software publisher" thus embraces much morethan a motion picture company, and the term "carrier" embraces much morethan a digitally encoded optical disk.

SUMMARY OF THE INVENTION

In accordance with the principles of the invention, all signals arerepresented by respective bit streams. Successive data blocks maycontain a sufficient number of video bits to represent multiple frames,but not necessarily a number of frames or a number of bits which is thesame for each block. In fact, it is not necessary that a block containany data which represents image frame information. Similarly, a blockmay contain data which represents one or more soundtracks, with the bitsnot necessarily representing the same time duration for each soundtrack;it is also possible that a particular soundtrack will not be representedat all in a particular block, while other soundtracks may be. Ifsubtitle information is provided, it too is represented in the datablocks. If subtitles are provided in multiple languages from which theuser selects one, it is possible for the different-language subtitlescorresponding to the same scene being contained in totally differentdata blocks. The basic operating principle is that the bit rate(represented by the number of bits read from the disk per unit time) foreach signal is a function of that signal rather than a function of a bitrate requirement for the disk as a whole. Because the number of bits foran individual signal that are stored in a particular data block mayrange from none to many (where "many" means many relative to the numberof bits stored for other signals), each data block identifies the kindsof bit information stored in it, and the bits representing one signalare delineated from bits representing another. But as long as it is madeclear what each group of bits in a data block represents, each signalcan enjoy its own data rate to thereby maximize efficient use of theoverall bit capacity of the disk.

This is not to say that a large group of data blocks should be used tostore video information, a succeeding large group should be used tostore audio information, etc. Such a scheme is possible withsufficiently long buffers, but the buffers would be needlessly long.There is a different buffer provided in the player for each signal to begenerated from the disk, with the bits representing each signal beingloaded into a respective buffer as they are read, and with each signalbeing generated by reading bit information from the respective buffer atthe proper rate. Because the several signals are usually synchronizedwith each other, the several bit streams must be processed in asynchronized manner. This means that there must always be bits availablein the buffers for all signals as they are required. This, in turn,means that while each buffer need not be kept full, it must alwayscontain enough bits for immediate needs. At the other extreme, thereading of data blocks must stop when any buffer is full because anybits fed to that buffer will be lost (or they will replace other bits inthe buffer which will be lost). Consequently, the required hardwarecontrol is that reading of data blocks temporarily cease when any bufferis full, with the bits representing different signals being distributedamong the data blocks such that every buffer at all times has asufficient number of bits for immediate needs.

The invention is disclosed in the context of an overall system whichoffers numerous advantageous features. The entire system is describedalthough the appended claims are directed to specific features. Theoverall list of features which are of particular interest in thedescription below include:

Video standard and territorial lock out.

Play in multiple aspect ratios.

Play of multiple versions, e.g., PG-rated and R-rated, of the samemotion picture from the same disk, with selective automatic parentaldisablement of R-rated play.

Encrypted authorization codes that prevent unauthorized publishers fromproducing playable disks.

Provision of multiple-language audio tracks and multiple-languagesubtitle tracks on a single disk, with the user specifying the languageof choice.

Provision of multiple "other" audio tracks, e.g., each containing somecomponent of orchestral music, with the user choosing the desired mix.

Variable rate encoding of data blocks, and efficient use of bit capacitywith track switching and/or mixing, to allow all of the abovecapabilities on a single carrier.

Further objects, features and advantages of the invention will becomeapparent upon consideration of the following detailed description inconjunction with the drawing, in which:

FIG. 1 depicts a prior art system and typifies the lack of flexibilityin, and the poor performance of, presently available media players;

FIG. 2 depicts the illustrative embodiment of the invention;

FIG. 3 is a chart which lists the fields in the lead-in portion of thedigital data track of an optical disk that can be played in the systemof FIG. 2;

FIG. 4 is a similar chart which lists the fields in each of the datablocks which follow the lead-in track section of FIG. 3;

FIGS. 5A-5E comprise a flowchart that illustrates the processing by thesystem of FIG. 2 of the data contained in the lead-in track section ofan optical disk being played;

FIG. 6 is a flowchart that illustrates the processing of the datablocks, in the format depicted in FIG. 4, that follow the lead-insection of the track;

FIG. 7A is a state diagram and legend that characterize the manner inwhich the player of the invention reads only those data blocks on a disktrack that are required for the play of a selected version of a motionpicture or other video presentation, and FIG. 7B depicts the way inwhich one of two alternate versions can be played by following the rulesillustrated by the state diagram of FIG. 7A;

FIG. 8 depicts symbolically a prior art technique used in compressingthe digital representation of a video signal; and

FIG. 9 illustrates the relationships among three different image aspectratios.

THE PRIOR ART

The limitations of the prior art are exemplified by the system ofFIG. 1. Such a system is presently available for playing a single sourceof program material, usually a VHS videocassette, to generate a videosignal conforming to a selected one of multiple standards. A system ofthis type is referred to as a multi-standard VCR, although stand-alonecomponents are shown in the drawing. Typically, a VHS tape 7 hasrecorded on it an NTSC (analog) video signal, and the tape is played ina VHS player 5. The analog signal is converted to digital form in A/Dconverter 9, and the digital representations of successive frames arewritten into video frame store 11. Circuit 13 then deletes excessframes, or estimates and adds additional frames, necessary to conform tothe selected standard, e.g., PAL. To convert from one standard toanother, it is generally necessary to change the number of horizontallines in a field or frame (image scaling). This is usually accomplishedby dropping some lines, and/or repeating some or averaging successivelines to derive a new line to be inserted between them. The mainfunction of circuit 13, of course, is to convert a digital framerepresentation to analog form as the video output.

Systems of the type shown in FIG. 1 generally degrade the video output.Conventional videocassettes deliver reduced quality video when theysupport more than one video standard. One reason is that there is adouble conversion from analog to digital, and then back again. Anotheris that the image scaling is usually performed in a crude manner(deleting lines, repeating lines and averaging lines). There are knownways, however, to perform image scaling in the digital domain withoutdegrading the picture. While not generally used, the technique is in theprior art and will therefore be described briefly as it is also used inthe illustrative embodiment of the invention.

To give a concrete example, the PAL standard has 625 lines per frame,while the NTSC standard has 525 lines per frame. Because no part of theimage is formed during the vertical retrace, not all of the horizontalline scans in either system are usable for representing imageinformation. In the PAL standard there are nominally 576 lines per framewith image information, and in an NTSC frame there are nominally 483lines with image information.

To convert from one standard to another, successive fields are firstde-interlaced. Then 576 lines are converted to 483, or vice versa, andre-interlaced. How this is done is easy to visualize conceptually.Consider, for example, a very thin vertical slice through a PAL frame.The slice is broken down into its three color components. Image scalingfor converting from PAL to NTSC, from a conceptual standpoint, isnothing more than drawing a curve based on 576 PAL pieces of color dataand then dividing the curve into 483 parts to derive a piece of data foreach horizontal line of the desired NTSC signal. In actuality, this isaccomplished by a process of interpolation, and it is done digitally.(Image scaling, in general, may also involve a change in the aspectratio, for example, in going from HDTV to NTSC, and may require clippingoff information at both ends of every horizontal line.)

While prior art systems thus do provide for standards conversion, thatis about the extent of their flexibility. The system of FIG. 2, on theother hand, offers unprecedented flexibility in ways not evencontemplated in the prior art.

THE ILLUSTRATIVE SYSTEM OF THE INVENTION

The system of FIG. 2 includes a disk drive 21 for playing an opticaldisk 23. Digital data stored on the disk appears on the DATA OUTconductor 25. The disk drive operation is governed by microprocessordisk drive controller 27. The read head is positioned by commands issuedover HEAD POSITION CONTROL lead 29, and the speed of the disk rotationis governed by commands issued over RATE CONTROL conductor 31. Opticaldisks are usually driven at either constant linear velocity or constantangular velocity. (Another possibility involves the use of a discretenumber of constant angular velocities.) Disks of the invention may bedriven at constant linear velocity so that the linear length of tracktaken by each bit is the same whether a bit is recorded in an inner orouter portion of the track. This allows for the storage of the mostdata. A constant linear velocity requires that the rate of rotation ofthe disk decrease when outer tracks are being read. This type of opticaldisk control is conventional. For example, the CD audio standard alsorequires disks which are rotated at a constant linear rate.

Microprocessor 41 is the master controller of the system. As such, itissues commands to the disk drive controller over conductor 43 and itdetermines the status of the disk drive controller over conductor 45.The disk drive controller is provided with two other inputs. Blocknumber/pointer analyzer 47 issues commands to the disk drive controllerover conductor 49, and BUFFER FULL conductor 51 extends a control signalfrom OR gate 54 to the disk drive controller. These two inputs will bedescribed below. (In general, although reference is made to individualconductors, it is to be understood that in context some of theseconductors are in reality cables for extending bits in parallel. Forexample, while the output of OR gate 54 can be extended to the diskdrive controller over a single conductor 51, block number/pointeranalyzer 47 could be connected to the disk drive controller over a cable49 so that multi-bit data can be sent in parallel rather than serially.)

An important feature of the system of FIG. 2 is that bit information isstored on the disk at a rate which varies according to the complexity ofthe encoded material. By this is meant not that the number of bits persecond which actually appear on the DATA OUT conductor 25 varies, butrather that the number of bits which are used per second varies. Videoinformation is stored in compressed digital form. FIG. 8 shows themanner in which video frames are coded according to the MPEG1 and MPEG2standards. An independent I-frame is coded in its entirety. Predicted orP-frames are frames which are predicted based upon preceding independentframes, and the digital information that is actually required for a Pframe simply represents the difference between the actual frame and itsprediction. Bidirectionally predicted B-frames are frames which arepredicted from I and/or P frames, with the information required for sucha frame once again representing the difference between the actual andpredicted forms. (As can be appreciated, fast forward and fast reversefunctions, if desired, are best implemented using I-frames.) The numberof bits required to represent any frame depends not only on its type,but also on the actual visual information which is to be represented.Obviously, it requires far fewer bits to represent a blue sky than itdoes to represent a field of flowers. The MPEG standards are designed toallow picture frames to be encoded with a minimal number of bits. Frameinformation is required at a constant rate. For example, if a motionpicture film is represented in digital form on the disk, 24 frames willbe represented for each second of play. The number of bits required fora frame differs radically from frame to frame. Since frames areprocessed at a constant rate, it is apparent that the number of bitswhich are processed (used) per second can vary from very low values tovery high values. Thus when bits are actually read from the disk, whilethey may be read from the disk at a constant rate, they are notnecessarily processed at a constant rate.

Similar considerations apply to any audio stored on the disk. Any datablock may contain the bit information required for a variable number ofimage frames. Any data block may similarly contain the bit informationrequired for a variable time duration of a variable number of evennumerous audio tracks. (There is just one physical track. The referenceto multiple audio tracks is to different series of time-division slicescontaining respective audio materials.) The audio tracks contain digitalinformation, which may also be in compressed form. This means that ifthere is information stored in any data block for a particular audiotrack, those bits do not necessarily represent the same time duration.It might be thought that the duration of the sound recorded for anyaudio track corresponding to any picture frames represented in a blockwould be the duration of the picture frames. However, that is notnecessarily true. This means that audio information may be read beforeit is actually needed, with the reading of more audio informationpausing when a sufficient amount has already accumulated or with audionot being included in some data blocks to compensate for the precedingover-supply. This leads to the concept of buffering, the function ofaudio buffers 53, video buffer 55, pan scan buffer 57, subtitle buffer59, and OR gate 54 which generates the BUFFER FULL signal.

As each data block is read from the disk, it passes through gate 61,provided the gate is open, and the bit fields are distributed bydemultiplexer 63 to the various buffers and, over the COMMAND/DATA line65, to master controller 41. Each data block in the illustrativeembodiment of the invention contains video bit information correspondingto a variable number of picture frames. As discussed above, there may bea large number of bits, or a small number, or even no bits (for example,if the particular disk being played does not represent any video).Successive groups of video data are stored in video buffer 55 separatedby markers. Video decoder 67 issues a command over conductor 69 when itwants to be furnished with a new batch of data over conductor 71.Commands are issued at a steady rate, although the number of bitsfurnished in reply vary in accordance with the number of bits requiredfor the particular frames being processed. The rate at which bits areread from the disk drive is high enough to accommodate frames whichrequire maximal information, but most frames do not. This means that therate at which data blocks are actually read is higher than the rate atwhich they are used. This does not mean, however, that a well-designedsystem should delay reading of a block of data until the data isactually required for processing. For one thing, when data is actuallyrequired, the read head may not be positioned at the start of thedesired data block. It is for this reason that buffering is provided.The video buffer 55 contains the bit information for a number ofsuccessive frames (the actual number depending upon the rate at whichbits are read, the rate at which frames are processed, etc., as is knownin the art), and video data block information is read out of the videobuffer at a constant frame rate determined by video decoder 67. Videodata is delivered to the buffer only until the buffer is full. Once thebuffer is full, no more information should be delivered because itcannot be stored. When the video buffer is full, a signal on conductor69 causes the output of OR gate 54 to go high to inform disk drivecontroller 27 that one of the buffers is full.

Similar remarks apply to the three other types of buffers. (There is asingle subtitle buffer 59, a single pan scan buffer 57, and numerousaudio buffers 53, the purpose of all of which will be described below.)When any of these buffers is full, its corresponding output causes ORgate 54 to control the BUFFER FULL conductor to go high and to so informthe disk drive controller that one of the buffers is full. Audio buffers53 and subtitle buffer 59 operate in a manner comparable to thatdescribed for video buffer 55. Audio processor decoder 71 issues acommand to the audio buffers when it requires audio track data, at whichtime the audio buffers furnish such data. Similarly, graphics generator73 retrieves data from subtitle buffer 59, and pan scanprocessor/vertical scaler 87 receives data from pan scan buffer 57 aswill be described below.

When any one of the four buffers is full (which includes any one of theindividual buffers within the block 53), the disk drive controller 27causes the disk drive to stop reading data. Data is not read again untilall of the buffers can accept it, i.e., until no buffer is full andconductor 51 goes low. (Conversely, if the buffers are being depleted ofdata too rapidly, an adjustment in the RATE CONTROL signal on conductor31 increases the disk speed and thus the rate at which the buffers arefilled.)

This discussion of buffering arose from a consideration of the BUFFERFULL input 51 to the disk drive controller 27. The other input whichremains to be described is that represented by cable 49. As will bedescribed below, every data block has a serial block number as well aspointer information at its beginning. Circuit 47 reads the serial blocknumber and analyzes the pointer information. The pointer, a serial blocknumber, points to the next data block which should be read. Thisinformation is furnished to the disk drive controller over cable 49. Itis in this way that the disk drive controller can control positioning ofthe read head of the disk drive so that the desired data block can beaccessed. Many times the wrong block will be read--this is to beexpected in the case of a jump to a new block, as is the case, forexample, when a jump is made from one track to another when playing a CDaudio disk. If the disk drive reads a data block whose serial blocknumber is too high or too low, this is determined by blocknumber/pointer analyzer 47 which then issues a new command over cable 49to the disk drive controller to cause it to read another block with alower or higher serial block number respectively. During the time thatthe read head is positioning itself to read a new block, the data whichis read is not actually used. Gate 61 remains closed so that theinformation is not delivered to the demultiplexer 63 for distribution tothe four buffers and to the master controller 41 over the COMMAND/DATAlead. It is only when the correct data block is reached, as determinedby circuit 47 analyzing the serial block number at the start of theblock, that conductor 75 is pulsed high to open gate 61.

The remainder of the block is then delivered to the demultiplexer. Thedata bits read from the disk are also delivered to the microprocessormaster controller 41 over conductor 77. Each data block contains notonly bit information which must be distributed to the various buffers,but also control information, e.g., bits that identify the kind of dataactually to be found in the block. The identification bits (flags andthe like, as will be described below) are furnished to the mastercontroller so that it is in control of the system at all times. Theidentification bits are used by the demultiplexer to control datadistribution to the various buffers. (The master controller issuescommands over conductor 76 to the block number/pointer analyzer 47 whichexercise not only general control over this element, but also specificcontrol by causing element 47 to turn off the enabling signal onconductor 75 as is appropriate to prevent full data blocks from enteringthe demultiplexer if they are not required for subsequent processing.)

The master controller is at the heart of the system and in fact carriesout the bulk of the processing to be described below. The user of theplayer communicates with the master controller via an interface 79,typically a keyboard. The user also is provided with a key and lockmechanism, shown symbolically by the numeral 81, which is referred toherein as the "parental lock" option. If the lock is turned on, thenR-rated motion pictures will not play. The manner in which this iscontrolled by bits actually represented on the disk will be describedbelow. If the lock is on, and only an R-rated picture is on the disk, adisabling signal on PARENTAL LOCK CONTROL conductor 83 closes gate 61.No data bits are transmitted through the gate and the disk cannot beplayed. As will become apparent below, if the disk also has on it aversion of the film which is not R-rated, it will play if it is selectedby the viewer. Although the parental lock feature is shown as requiringthe use of an actual key and lock, it is to be understood that thefeature can be implemented by requiring keyboard entries known only to achild's parents. The manner of informing the master controller thatR-rated versions of a motion picture should not be viewed is notrestricted to any one form. Just as physical keys and coded keys arealternatively used to control access to a computer, so they can be inthe system of FIG. 2. What is important is the way in which twodifferent versions can be represented on the same disk (withoutrequiring the full version of each), and how the system determineswhether a selected version may be played in the first place. This willbe described below.

Master controller 41 includes several other outputs which have not beendescribed thus far. Conductor 85 represents a MASTER CLOCK bus which isextended to all of the sub-systems shown in FIG. 2. In any digitalsystem, a master clock signal is required to control the proper phasingof the various circuits. The six other outputs of the master controllerare extended to demultiplexer 63, audio processor decoder 71, pan scanprocessor/vertical scaler 87, video frame store, interlace and 3:2pulldown circuit 89, graphics generator 73, and sync generator and DVAconverter 92. These are control leads for governing the operations ofthe individual circuit blocks.

Audio processor decoder 71 processes the data in buffers 53 and derivesindividual audio analog signals which are extended to anamplifier/speaker system shown symbolically by the numeral 91. Videodecoder 67 derives a DIGITAL VIDEO signal on conductor 93 from thecompressed video data which is read from buffer 55. The digital video isfed to pan scan processor/vertical scaler 87 frame by frame. Theparticular video coding/decoding that is employed is not a feature ofthe present invention. A preferred standard would be one along the linesof MPEG1 and MPEG2, but these are only illustrative. The same is true ofthe audio track coding. The present invention is not limited toparticular coding methods.

The operations of circuits 57 and 87 can be best understood by firstconsidering the symbolic drawing of FIG. 9. The digital informationwhich is stored on the optical disk in the preferred embodiment of theinvention characterizes frames having a "master" aspect ratio of 16:9,the so-called "wide screen" image. The master aspect ratio is shown onthe upper left in FIG. 9. If the ultimate analog signal to be displayedon the user's television receiver requires this aspect ratio, and thenumber of horizontal scan lines with picture information (as opposed tohorizontal scan lines which occur during vertical retrace) correspondswith the number of horizontal lines represented by the video bitinformation stored on the disk, then the generation of the video analogsignal is straightforward. But if the television receiver of the useraccommodates a TV signal having a 4:3 aspect ratio, and the masteraspect ratio on the disk is 16:9 rather than 4:3, then there are twochoices. One is to display the original picture in "letter box" form. Asdepicted on the right side of FIG. 9, what is done in this case is tovertically compress uniformly a master image so that its horizontaldimension fits into the confines of the television receiver. Thisresults in the vertical dimension being shortened at the same time sothat it fills less than the full height of the TV display area. Whatthis means is that the horizontal line scans at the top and bottom ofeach overall frame must be blanked, with dark bands forming in theirplace--but the original aspect ratio is preserved. The other option isfor a "pan scan" reduced aspect ratio. What this involves issuperimposing a box having a 4:3 aspect ratio on the original widescreen image. As a result, the left side of the picture, the right side,or both sides, are clipped off. (In all cases, even if a wide screenimage corresponding to a 16:9 master aspect ratio is to be shown, it maybe necessary to form a number of horizontal line scans which isdifferent from the number of horizontal lines represented on the disk.The number of horizontal lines is a function of the video signalstandard to which the video output must conform. Changing the number oflines is a process known as vertical scaling, as described above.)

With respect to pan scan processing, it will be apparent from FIG. 9that in order to identify that portion of a 16:9 master aspect ratiopicture which should be used to form a pan scan reduced aspect ratiopicture, all that is required is to specify the starting point alongeach horizontal line scan of the information that should be used.Specifying a single number (e.g., column 200 out of a total of 960columns) suffices for this purpose. The issue, however, is whether thesame column is always used. In some cases the player may be told that ifa 4:3 aspect ratio is desired, it should always be taken from the middleof the wide screen image. In other cases, a variable column startingpoint may be desired, in which case a data block actually containsinformation which represents the starting column number which should beused from that point until another change is effected.

As will become apparent below, the video information in each data blockincludes a flag which represents whether the pan scan column informationshould be updated. If there is such a flag, video decoder 67 issues acommand over conductor 95 to pan scan buffer 57. At this time the bufferaccepts a pan scan update from demultiplexer 63. That update remains inthe buffer, for use by pan scan processor/vertical scaler 87 with thesucceeding frames, until another change takes place.

It is in pan scan processor/vertical scaler 87 that the number ofhorizontal lines is adjusted and the aspect ratio is changed. Thedigital video is furnished by video decoder 67 and the pan scaninformation, if it is required, is provided by buffer 57. The output ofcircuit 87 consists of uncompressed digital video, in the desired aspectratio and represented by the number of horizontal lines required for theselected television standard.

Once video frame information is stored digitally in frame store 89, itcan be broken up into interlaced fields if the selected standardrequires it. Also, 3:2 pulldown is the technique used to convert24-frames-per-second motion pictures to 60-fields-per-second video (thenominal values of 24 and 60 are in reality 23.97 and 59.94); to convertdata representative of a motion picture to an NTSC format, frameinformation (data blocks) must be read at the rate of 24 per second. (Asis standard in the art, such a transformation applies frame 1 of thesource material to fields 1, 2 and 3 of the video signal, frame 2 of thesource material to fields 4 and 5 of the video signal, frame 3 of thesource material to fields 6, 7 and 8, etc., thus yielding 60 fields for24 original frames.) On the other hand, conversion to the PAL standardis relatively simple, and 3:2 pulldown is not required. The PAL standardrequires 50 fields per second. Frames are processed at the rate of 25per second, and every frame is used to form two fields. (Because motionpicture films are shot at the rate of 24 frames per second yet processedat the rate of 25 per second when converting to PAL, everything whichoccurs on the TV screen takes place 4% faster in Europe than it does inthe United States.) Whether the frames are processed at the rate of 25per second or 24 per second is controlled by changing the frequency ofthe MASTER CLOCK signal on bus 85.

The output of block 89 is digital, and is extended to sync generator andD/A converter 92. It is in this element that appropriate sync pulses areinserted into the fields, and the digital information is converted toanalog. Any subtitles that are required are contained in buffer 59.Under control of microprocessor 41, commands are issued over controllead 97 to graphics generator 73. This conventional circuit retrievescoded character information from the subtitle buffer, and generates aVIDEO signal on conductor 99 which depicts the subtitles. The KEY signalis generated on conductor 98, and the two signals are extended to aconventional keyer circuit 96. This device merges the subtitles with thevideo image (utilizing hard or linear keying at the manufacturer'soption, as is known in the art), and extends the composite video signalto a conventional TV display device 94.

LEAD-IN TRACK FIELDS

Before proceeding with a description of the detailed processing, it willbe helpful to consider the information which is stored in the lead-inportion of the disk track. This information is stored in individualfields as depicted in FIG. 3, and it is this information which controlssubsequent processing of the data read from the disk. The format of adata block is shown in FIG. 4, but for an understanding of how the datain this block is used, it is necessary to appreciate the set-upinformation which is read first.

Referring to FIG. 3, at the start of the track there are a number oflead-in sync bits. Although for all other entries minimum and maximumnumbers of bits are depicted in the appropriate columns, no such numbersare provided for the lead-in sync bits. The number of sync bits requiredat the beginning of the track depends on the hardware employed. Giventhe particular hardware and range of disk speeds involved, a sufficientnumber of sync bits are provided at the start of the track to allow thecircuits involved with reading the disk, including disk drive controller27 and block number/pointer analyzer 47, to synchronize themselves tothe bit stream on DATA OUT conductor 25. Bit synchronization is atechnique well known in digital systems.

The second field consists of 40 bits representing authorizedterritories. There are several ways in which software publishers canlock out play of their software. The most important involve controllingwhether R-rated motion pictures can be played (the parental lock outoption), and whether the final analog output video signal can assume thestandard selected by the user. It is in this way, for example, that asoftware publisher might allow a motion picture to be played on an NTSCreceiver but not a PAL receiver. But as long as the player is providedwith this kind of lock out control, it can be extended to territories.All players used with the disks of the invention conform to the same setof specifications. One feature of the design is that each player isprovided with a representation of the territory or territories for whichit has been intended for sale. For example, the territory or territoriescan be represented by the settings of a DIP switch, a code stored in amicroprocessor ROM (e.g., in master controller 41) or the like. It isassumed that there are a total of 40 possible territories. Each disk hasa 40-bit field in its lead-in section, each bit of which is associatedwith one of the 40 territories. A 1 in any bit position is an indicationthat the disk is authorized for play in the respective territory, and a0 is an indication that it is not. A player whose code indicates that itis for sale in China, for example, will not play a disk if there is a 0in the 40-bit territory field at the position associated with China.

As an example of the use of such a feature, consider a player intendedfor sale in a particular country. A software publisher might put out amotion picture film which for contractual reasons is not to be releasedin that country. It is for this reason that a 0 would be stored in thebit position associated with that country in the authorized territoriesfield of the lead-in section of the track. Upon sensing this bit, mastercontroller 41 would cause circuit 47 to generate an inhibit signal onconductor 75 which would permanently cause gate 61 to block all datafrom passing through it.

The third field is a single bit, a flag which indicates whether there isany information in the following field. This information is termedherein "special software." The player of FIG. 2 ordinarily executes thesame software code, typically contained in read-only memory. It is thiscode which will be described in connection with the flowcharts of thedrawing. However, since the player is microprocessor controlled, thereis no reason why it cannot be used for some even totally unrelatedpurpose, and this can be enabled simply by loading software from thedisk. If the special software flag is a 1, then master controller 41reads on conductor 77 the software which immediate follows in field 4.Thus depending on whether the special software flag is a 0 or a 1, thefourth field is either empty or contains software of undeterminedlength. At the end of the software there is a sync word which is uniquein the sense that this word is not allowed to occur anywhere in theoverall data stream. When the sync word pattern appears, it is anindication that the preceding data field has come to an end, and a newfield follows. (In the event data having the sync word pattern wouldotherwise appear in the data stream and be misinterpreted as a syncword, it can be avoided using known techniques. For example, if the syncword consists of 32 bits of a predetermined pattern, and some overalldata sequence includes this pattern within it, then after 31 bits of thedata pattern are recorded, an extra bit, having a value opposite that ofthe last bit in the sync word pattern, may be inserted in the bitstream. When the player sees this bit, it discards it and treats thefollowing bit as a data bit instead of the last bit of the sync word.)

An example of special software might be software for controlling videogames. While the player is provided with an operating system designedfor the play of motion pictures and multi-track audios, it is certainlyfeasible for the player to perform additional and/or different functionsinvolved in the play of video games. This is especially true if the userinterface is detachable and joysticks and the like may be connected inplace of a keyboard to accommodate game-playing peripheral equipment.The system can be converted to a video game player simply by storing thenecessary software as it is read from the disk. While in the flowchartsto be described below the special software is shown as beingself-contained and not involving the standard processing steps, thespecial software can certainly call operating system subroutines forexecution in order to take advantage of the built-in code.

The fifth field consists of 12 bit positions, each corresponding to adifferent standard. Standards include 1250-line European HDTV, 1125-lineJapanese HDTV, 1050-line proposed American HDTV (as well as 1080-lineand 787-line proposed standards), 625-line PAL, 525-line NTSC, 625-lineSECAM, 360-line "letter box", etc. It is even possible to accommodatefuture standards, although to form an appropriate video signal in such acase different software would be required. However, that simply entailsproviding software on a disk to supplement the built-in operatingsystem.

As a single example, if the first bit position of the 12-bit fieldcorresponds to the NTSC standard, and if the user selects an NTSCstandard for play on his TV receiver, or if that is his default setting(as will be discussed below), then an NTSC signal will be generated onlyif the first bit in the authorized standards field is a 1.

Field 6 always contains 100 bits. These bits represent respective audiolanguages--dialog--for a motion picture. It is rare that so manyforeign-language versions of the same motion picture will be prepared,and it is not contemplated that so many versions will actually beincluded on a disk. In fact, there are a maximum of 16 audio trackswhich can contain dialog in different languages. Each of the 100 bits,except the first, represents one of 99 languages. If there is a 1 in thecorresponding bit position, it is an indication that there is an audiotrack with dialog in the corresponding language.

The first of the 100 bit positions does not really correspond with alanguage. Instead, a 1 in the first bit position means that there is amusic and effects ("M&E") track. (By "effects" is meant such things asthe sound associated with thunder, gunshots and the like.) As indicatedin the Comments field on FIG. 3, there are N "1"s in field 6 of thelead-in section of the overall track, where N has a maximum value of 16(one M&E track and up to 15 dialog tracks, or up to 16 dialog trackswithout M&E). As a single example, suppose that the third bit positioncorresponds with French, the fifth corresponds with Greek, and the100-bit field is 10101000 . . . 0. This means that there is an M&Etrack, as well as French and Greek dialog tracks. It does not mean thatevery single data block on the disk includes bit information whichrepresents M&E, and French and Greek dialog. What it does mean is thatany data block has at most three audio tracks with M&E and/or dialog. Italso means that any data block which has such audio track informationcontains the information in the order M&E, French, Greek. Just how thesystem determines which specific data blocks contain audio informationfor those languages represented in the 100-bit field will be describedbelow in connection with the fields contained in a data block.

It should be understood that the language audio tracks do notnecessarily include just dialog. As will be described shortly, it ispossible to mix an M&E track with a French dialog track, with the resultbeing a complete audio track suitable for play in France. But it iscertainly possible that a particular audio track will include pre-mixedM&E and original dialog. For example, if bit position 10 of the 100-bitfield represents English dialog and there is a 1 stored there, it meansthat there is an English language version of audio on the disk. However,it is possible that in the corresponding audio track there is not onlyEnglish dialog, but a full sound track including the M&E. At the sametime, there may be M&E in a separate track, if there is a 1 in the firstbit position of the 100-bit field. How the various tracks are processedin order to derive a complete sound track for play in any given languagedepends on subsequent information. Field 6 simply represents which audiolanguages are available, as well as whether there is a separate M&Etrack (without any dialog).

There is another piece of information which is necessary in order forthe audio scheme to function, and that information is represented infield 7. For each of the N available audio language tracks (up to amaximum of 16), there is a 3-bit code in the seventh field. Beforedescribing the meaning of the codes, it must be understood how the codesare associated with particular tracks and languages. Suppose that field6 is 101010000100 . . . 0 which is interpreted to mean that there is anM&E track, a French track, a Greek track and an English track. From thisinformation alone, there is no way to tell whether there is even any M&Ein the French, Greek and English tracks. All that is known language-wiseis that dialog is available in only three languages. For this example,there would be 12 bits in field 7. The first three bits are associatedwith the M&E track, the second three bits are associated with the Frenchtrack, and the third and fourth 3-bit codes are associated with theGreek and English tracks respectively. The 3-bit codes are as follows:

000--mixing master (M&E)

001--switching master (M&E)

010--dialog+(M&E), complete audio track

011--track to be mixed with mixing master

100--track to be switched with switching master

These five codes are all that are necessary to form complete soundtracks in the three available languages, French, Greek and English. Howthe tracks are combined will be described below, but what should beborne in mind is that the purpose of the entire arrangement is toprovide sound tracks in many languages (up to 15), without requiringwhat might be a 2-hour audio recording for each. In fact, if a movie istwo hours long, but the actual dialog is only 30 minutes, the goal is torecord one full track (M&E or original sound track), with only a30-minute audio recording of dialog for a particular language.

Field 8 contains N×4 bits, that is, 4 bits for each of the N "1"s infield 6. There is thus a 4-bit code in field 8 for each audio languagetrack which is available on the disk. The 4-bit code represents thetrack type, and there are a maximum of sixteen possibilities. Typicaltrack types are single-channel mono, two-channel Dolby, 5.1-channelMusicam, etc. [The term 5.1-channel refers to left, right, center, leftrear and right rear channels, together with a sub-woofer channel.] The4-bit track type codes allow the master controller to determine themanner in which audio processor decoder 71 operates on the data in theup-to-16 audio tracks to derive analog outputs for speaker system 91.

Considering again field 7, there are several ways in which a completesound track, in a selected language, can be derived from the disk. Theoperation of mixing involves mixing (adding together) two sound tracks.The operation of switching involves switching between two sound tracks,and playing only one of them at any given time. The first track isalways M&E, if it is available. The code for this track is always 000 or001. If the code is 000, it means that there is no dialog in the trackand its M&E is to be mixed with the selected language track. If the code011 is associated with the French track, for example, it means that thefirst and third tracks should be mixed at all times. The dialog, whenthere is dialog, appears in the French track, and mixing it with themixing master provides a complete French sound track. On the other hand,the first track may be a switching master. What this means is that musicand effects are recorded in this track, with or without dialog. TheFrench track in this case would be represented by a 100 code. Itcontains M&E and dialog, but only when there is dialog. The M&E track,the first, is played alone when there is no dialog, but the fifth trackis played alone when there is. The tracks are switched, not mixed. TheFrench track, when dialog is recorded in it, includes not only dialogbut M&E as well since this would be the only source of M&E in a switchedtype operation.

The fifth possibility (010) is that a particular track happens tocontain the original sound track, M&E together with dialog in theoriginal language. If the dialog is in the selected language, the trackcan be played from beginning to end, by itself. This track can alsoserve as a switching master (code 001) for other languages.

When it comes to mixing tracks, whatever audios are in the two specifiedtracks (the mixing master and the track which is mixed with it) aresimply added together at all times; whatever audio there is in the twotracks gets played. It is only when switching between the switchingmaster and the track with which it is switched that one track getsplayed in lieu of the other. It is true that each track may containaudio information only when the other does not (which would allowmixing), but it is conceivable that the switching master will alsoinclude dialog, i.e., if it is a recording of the original sound trackof the motion picture. That is why switching is employed--only one trackis heard from at any given moment. As will be described below, each datablock includes bits which inform the master controller which audiotracks actually contain data in that block. If a selected audio languagetrack with an original 100 track code has data in any data block, thenthe audio processor decoder 71 processes the data in that audio track tothe exclusion of any data which might be in the switching master track.

Field 9 on FIG. 3 contains six bits which are coded to represent anumber M. This is the number of "other" audio tracks, separate and apartfrom the up-to-16 audio language tracks. The usual use for these tracksis to represent, in compressed digital form, individual instruments ormixes of instruments, with the user having the option of combining them.In an extreme form, there could be 63 separate instrumental tracks, withthe user being able to combine any tracks he desires, and to set theirrelative levels before mixing. If one of the tracks contains thecombined sound to begin with, it is possible to delete an instrumentfrom the orchestral mix by specifying that its information contentshould be deleted, or subtracted, from the orchestral mix. This wouldallow a user, for example, to play his piano to the accompaniment of anorchestra playing a concerto from which piano play has been eliminated.It would also allow a user to single out a particular instrument tofacilitate practice. Precisely what the user does with the "other" audiotracks is determined by menu selections which are made available to him.Field 8 simply identifies how many "other" audio tracks are present onthe disk. (The term "other" audio tracks would appear to be rathernon-descriptive, but this isn't the case. The intent is that the termsubsume any audio track usage other than the provision of sound tracksfor motion pictures. Rather than to have orchestral music in these"other" audio tracks, for example, it is possible to have individualvocalists, allowing a user to study different harmonizations.)

It is apparent that if there are indeed 63 "other" audio tracks, thenmuch if not most of the disk capacity may be allocated to audio data.But that is precisely why so many audio tracks are made available. It iscertainly contemplated that some disks playable in the system of FIG. 2will not include video. In fact, field 19, to be described below, is a1-bit field which informs the master controller whether there is anyvideo data at all on the disk.

Once it is determined that there are M "other" audio tracks, the nextfield specifies how each track is coded. As in the case of field 8, a4-bit code is used for each of the "other" audio tracks. Thus the numberof bits in field 10 can be as low as 0 (if there are no "other" audiotracks) or as high as 252 (63×4).

While the player can determine from reading fields 9 and 10 how many"other" audio tracks there are, the user has to be told what is in thesetracks in order that he know what to do with them. There is adescription of each track, and it is in multiple languages. The firstthing that the player must be given is a list of the languages in whichthere are descriptions of the "other" audio tracks. A 100-bit field isused for this purpose. As indicated in FIG. 3, field 11 has 100 bits. A1 in any bit position is an indication that track definitions areavailable in the respective language. The correspondence between bitpositions and languages is the same in field 11 as it is in field 6. Itwill be recalled that the first bit position in field 6 corresponds toM&E, not a traditional "language". The first bit position in field 11 isthus not used, and there can be at most 99 "1"s in field 11.

Before the track definitions are actually read and processed, the playermust determine what menu choices to provide the user. Suppose, forexample, that there are ten "other" audio tracks, each having sounds ofdifferent orchestral instruments. Once the track definitions in theselected language are made available to the operating system, it candisplay a standard menu to the user. The user can then pick particulartracks to be played together, particular tracks to be deleted, theirrelative sound levels, and other "standard" choices. However, in casethe "other" audio tracks do not represent orchestral music, or they dorepresent it but in a way that requires unusual menu selections, thestandard operating system software for interfacing with the user so thatthe system can determine what is to be done with the "other" audiotracks will not suffice. To accommodate unusual situations, theoperating system must be provided with special software for the creationof the menu, as well as to control how the selected tracks aremixed/deleted following user selections. The technique used is the sameas the technique described above in connection with loading specialsoftware for changing the overall operation of the player (fields 3 and4). Field 12 is a single bit. If it is a 1, it is an indication thatthere is a field 13 which contains special mixing/deletion software. Asindicated on FIG. 3, field 13 thus has anywhere from no bits to anundetermined number which is dependent on the length of the specialsoftware to be loaded into the machine from the disk. The specialsoftware ends with a sync word so that the player will know when thenext field begins.

The next field, field 14, consists of the track definitions themselves.Since there are M "other" audio tracks, and there are P languages inwhich they are to be defined for the user, P×M character strings arerepresented in field 14. Each string is separated from the next by anescape character. First there are M character strings (trackdefinitions) in the first language corresponding to the first positionin field 11 which contains a 1, then there are M character strings inthe second language corresponding to the second bit position in field 11which contains a 1, etc. As will be described below, the user informsthe player in which of the available languages the menu which includesthe track definitions should be displayed. While the entire DATA OUT bitstream from the disk drive is extended to the master controller in thesystem of FIG. 2, only the character strings corresponding to theselected language are processed. They are processed and displayed inaccordance with the standard software, or the special mixing/deletionsoftware which was just read from field 12 if such software is includedon the disk. (It should be noted that it is the function ofdemultiplexer 63 to distribute to the several buffers only therespective data bits that are intended for them. It is controller 41that tells the demultiplexer what to do after the controller interpretsthe information in both the lead-in track section and the individualdata blocks.)

As described in connection with FIG. 2, provision is made for theinsertion of subtitles. The language is selected by the user as will bedescribed, but the player must be told the languages in which subtitlesare available. Another 100-bit field is used for this purpose. Asindicated in line 15 of FIG. 3, the "1"s in the field represent theindividual languages available for subtitles. As is the case with theavailable display languages, there is a maximum of 99 since the firstbit position corresponds to M&E which is not strictly speaking a"language."

Field 16 is a 4-bit multiple version code. The player is informed notonly whether there are two versions of the same video presentation onthe disk, but also what the choices are with respect to them. The firstbit is a 0 if there is only one version on the disk, in which case thesecond and fourth bits are ignored. Bit 1 has a value of 1 if there aretwo versions on the disk. The second bit in the code tells the playerwhether the parental lock option is to be implemented, or whether adifferent criterion is to be used in selecting which version is played.The usual situation is where the parental lock option is implemented, inwhich case the bit in the second position of the 4-bit code is a 0. Thisinforms the player that it should determine whether the parental lockoption is "on." If it is, R-rated (or, more broadly, adult-rated)versions should not be played. The bit in position 3 of the code is anindication whether version A (the first or only version) is R-rated ornot (0=no, 1=yes), and the fourth bit in the code provides the sameinformation for version B if there are two versions; if there is onlyone version, the fourth bit is ignored. This is all the information theplayer needs to determine whether either or both of two versions can beplayed. When there are two versions of the same motion picture on thedisk, the user is asked to select one of them. But if the parental lockoption is "on" and one of the two versions is R-rated, the user is givenonly the choice of playing the non-adult version, or playing neither, aswill be described below. If both versions are R-rated and the parentallock option is "on", then the user can watch neither version.

On the other hand, it is possible that there will be two versions of thesame material on the disk, but it is not a question of one of them beingadult-rated and the other not. For example, one version might be ateaching film including questions and answers, and the other mightinvolve a test on the same subject matter including just questions. Forthe most part the two versions would be the same. In such a case, thefirst bit in field 16 would still be a 1 to indicate that two versionsare available, but the second bit would now be a 1 instead of a 0, toindicate that the choice between the two versions does not depend onwhether they are R-rated or not. A 1 in the second bit position is anindication that the third and fourth bits characterize the two versionsrespectively with respect to a characteristic other than rating.

What the third and fourth bits actually mean in this case, and what menuchoices are provided the user, has to be determined by resorting todifferent criteria. The same technique that was used twice previously isnow used once again--special software is provided along with the versioncodes. Field 17 consists of a single bit which serves as a flag toindicate whether special version software is available. If the bit is a1, then field 18 is read to access the software. As in the case of thetwo earlier software fields, field 18 terminates with a sync word toindicate the start of the next field. The special software controls amenu presentation that is unique for the particular disk.

The next field consists of a single bit. As indicated in FIG. 3, itinforms the player whether video data is available. If it isn't, itsimply means that there are no video data block fields in the overalldata blocks to be described in connection with FIG. 4.

Field 20 is a single bit, and it identifies the base or master aspectratio. If the bit has a value of 0, it is an indication that any videoon the disk has a 16:9 "wide screen" aspect ratio, as depicted in FIG.9. On the other hand, if the bit is a 1, it is an indication that theaspect ratio of the video on the disk is 4:3.

As described above, if the original video has a "wide screen" aspectratio, then there are two ways in which a 4:3 reduced aspect ratio canbe derived. One way is to form the video image from the middle part ofthe "wide screen" original. Another way is to "pan scan" in the sensethat the section of the original image which is actually utilized is notnecessarily always the middle part. In fact, FIG. 9 shows the use ofmore information on the left than on the right of the original image.Field 21 is a single bit which is indicative of pan scan availability.If field 20 is a 1, the base aspect ratio is 4:3 so that pan scanavailability is irrelevant--the single bit in field 21 is simplyignored. But if the base aspect ratio is 16:9 (field 20 has a 0), thevalue of the bit in field 21 tells the player whether the subsequentdata blocks provide starting column information which can be loaded intopan scan buffer 57 on FIG. 2. If the bit in field 21 is a 0, the datablocks do not include column number information, and if the video is tobe played in a 4:3 aspect ratio from a "wide screen" original, then thevideo image is formed from the middle part of each original frame. Onthe other hand, if pan scan information is available in the data blocks,then buffer 57 on FIG. 2 is updated as required and the final videoformed will have an added degree of variability.

Field 22 is a 20-bit number which represents the total number of datablocks on the disk. However, if there are two different versions, whilethey have many data blocks in common, the remaining numbers of blocks inthe two versions may be different. For example, a scene might becompletely omitted from one of the versions, in which case it would havea smaller total number of data blocks. For this reason, if field 16indicates that there are two versions of a motion picture or othersource material on the disk, field 23 provides the total number of datablocks in version A, and field 24 provides the total number of datablocks in version B. Both fields are omitted if there is only oneversion on the disk.

Each data block may include video information for a variable number offrames. The system could determine the total playing time from thenumber of data blocks (either the total number if there is only a singleversion, or two different numbers if there are two versions), only ifthe system is informed of the original frame rate and the average numberof frames represented in each block for the disk as a whole. Two diskswith the same number of data blocks will have different running times ifthe original source material for one of them was motion picture filmwhose frames were generated at the rate of 24 per second and the otherhad an original source material derived from a 30 frame-per-second videocamera. Field 25 is a 4-bit value that identifies the original framerate (24, 30, etc.), a number necessary for proper generation of thevideo signal. Although the time represented by each data block could bedetermined from the frame rate if each data block contains only oneframe, it is possible to store more or less than one frame of data ineach data block. Also, there may be no frame information at all, i.e.,the video availability flag in field 19 may be 0. Consequently, field 26is provided. This field contains a 10-bit number which represents theblock time factor, i.e., the average time duration represented by eachblock. Multiplication of the block time factor by the total number ofblocks (or the total number in a particular version) yields the runningtime. (In practice, the block time factor is about the same for bothversions on a disk. If desired, individual block time factors can beprovided.)

As is common practice with optical disks in general, the disk of theinvention may be provided with a table of contents for allowing the userto select a particular part to play, or simply to inform the user ofprecisely what is on the disk and how long each part takes to play.Field 27, if included, is a table of contents. If only one version ofthe source material is on the disk, then there is only one table ofcontents. Otherwise, there is an additional field 28 which consists ofthe table of contents for the second version. FIG. 3 sets forth thesub-fields in field 27.

For lack of a better term, the video presentation is divided up intowhat are called "chapters." For each chapter the table of contentsincludes an 8-bit chapter number, thus allowing a maximum of 255individual chapters. Following each chapter number there is a 20-bitstarting block serial block number. It will be recalled that all of thedata blocks on the disk are numbered serially. In other words, whiledata blocks may be common to both versions A and B, or unique to onlyone of them, the numbers of the data blocks are in serial order alongthe disk track. The table of contents includes the serial block numberof the data block which is the starting block for each chapter.

Similarly, in order to determine the play time for each chapter, thesystem must know how many blocks are included in each chapter. For thisreason, the next piece of information is a 20-bit block duration.Multiplying this number by the block time factor allows the play time ofeach chapter to be determined. Alternatively, the actual running timefor each chapter could be provided instead of the block duration. (Suchinformation could be provided for different versions and standards.)

In order to display the title of each chapter, language strings must beprovided. Once again, the system must be advised of the languages whichare available for displaying chapter titles so that the user mightselect one of them. The usual technique of providing a 100-bit block foridentifying available languages is employed.

Finally, the actual language strings for identifying individual chaptersare provided. Each string ends with an escape character to separate itfrom the next string. This is the same technique used in connection withthe "other" audio track definitions discussed above in connection withfield 14.

Field 29 has a minimum of 100 bits and a maximum of 1200 bits. It willbe recalled that there can be up to 12 authorized standards, i.e., thefinal video output can be in up to 12 different formats. In order toinsure conformance with quality standards agreed upon by allmanufacturers of players and all software publishers who have agreed tosupport a common set of specifications, it is possible to preventunauthorized software publishers from publishing disks which will playon players of the invention. Moreover, it is possible to limitparticular publishers to the manufacture of disks which will playaccording to only a sub-set of the 12 standards. For example, ifroyalties are to be paid on each disk which is manufactured according tothe agreed-upon specifications, and the royalties vary in accordancewith the number of standards according to which a disk can be played, itis possible to limit certain software manufacturers to only the sub-setof standards for which they have agreed to pay. For this reason, thereis an encrypted authorization code for each standard; the codes are allstored in field 29. The disk will play according to a particularstandard only if the proper encrypted authorization code is contained onthe disk. Field 29 includes 100 bits for each of the standardsauthorized in field 5. Since at least one standard must be authorizedthere are at least 100 bits. The maximum number of bits is 1200 if all12 standards are authorized.

The encryption scheme is based upon the principles of public-keycryptography. Public-key cryptography is by now well known, and aparticularly clear exposition of the subject is to be found in theAugust 1979 issue of Scientific American, in an article by Hellmanentitled "The Mathematics of Public-Key Cryptography." The use of apublic-key cryptosystem allows a message to be encrypted at site A inaccordance with a secret key, transmitted to site B, and decrypted atsite B in accordance with a public key. The secret key for encryptingthe message is known only to the transmitter. Such a scheme is typicallyused to authenticate a message. Upon decryption of the transmittedencrypted message at the receiving site, the message will beintelligible only if it was encrypted with the paired private key. Andsince the private key is private, if the decrypted message isintelligible, it must have originated with the owner of the private key.

Public-key cryptography is used in the invention in the following way.The actual data on the track is processed by the software publisher inaccordance with a predetermined algorithm. The details of the processingare not important. Any non-trivial processing that provides, forexample, a 100-bit result based on the disk data will suffice. The100-bit result is a "message" to be transmitted via the disk in anywherefrom one to twelve encrypted forms. There are 12 cryptosystem key pairs,each associated with a different one of the standards. The private keyfor the first standard authorized on the disk is used to encrypt the100-bit message and the 100-bit encryption is stored in field 29. Thisencryption is the authorization code for the particular standard. Thesame thing is done for all of the other standards authorized for theparticular disk, with the private key associated with each of thesestandards being used in each case.

The player operating system computes the same 100-bit result or messagethat was originally computed by the software publisher. The playersoftware then uses the public key associated with each of the standardsauthorized on the disk to decrypt the respective encrypted authorizationcode for that standard. The decrypted message should match the messagecomputed by the operating system after processing the disk data. If theydo not match, it is an indication that the software publisher did nothave the private key for encrypting the authorization code for theparticular standard, and the player will not produce a video signalaccording to that standard.

To explain this in another way, let it be assumed that the private keyfor authorized standard N on the disk gives rise to an encrypted messagePri_(N) (X), where X is a message to be encrypted. Similarly, thefunction Pub_(N) (X) represents the decryption of a function X using apaired public key. Let it further be assumed that the predeterminedalgorithm for processing the data on the disk is known by all playermanufacturers and software publishers, and gives rise to a 100-bitresult which is treated as a "message" M whose content (value) dependson the disk data. For standard N, the software publisher, after firstderiving M, stores on the disk the 100-bit encrypted authorization codePri_(N) (M). The player first derives the value M in the same way thatthe software publisher did. The player software then uses the public keyassociated with standard N for decrypting the encrypted authorizationcode. The operating system thus derives Pub_(N) (Pri_(N) (M)). Sincedecryption of an encrypted message should result in the originalmessage, the result of this decryption should be the same value M whichthe operating system derives by processing the disk data. If it is, thenthe particular standard is not only authorized, but the publisher hasthe right to authorize it. On the other hand, if the decryption of theencrypted authorization code M does not match the algorithmic result Mderived by the player (because the software publisher did not have theprivate key with which to derive Pri_(N) (M)), then that particularstandard is locked out.

While such a scheme works in the abstract, there is one practicalproblem which must be overcome. Suppose, for example, that the algorithmused to derive the original "message" M involves processing 20 datablocks on the disk with predetermined serial block numbers. (Theprocessing might be something as simple as multiplying by each othersuccessive groups of 100 bits each, and using as the result of eachmultiplication--for the next multiplication--only the 100 leastsignificant bits.) A publisher who is not empowered to authorizestandard N on a disk may nevertheless wish to do so. He does not knowthe private key with which to encrypt the derived value M which isapplicable to his software. Consequently, he does not know what 100-bitencrypted code he should put on the disk which will decrypt in a playerto the value M. But what he can do is copy the 20 predetermined datablocks from some other legitimate disk and put them on his own disk, andalso copy the encrypted authorization code in field 29. Those 20 datablocks, when processed in a player, will result in the value M, and itwill match the "stolen" encrypted authorization code after it isdecrypted in the player. Of course, the software publisher may havecommitted copyright infringement, but that simply compounds the felony.The practical problem which the software publisher faces is that he willhave data blocks which are "played" and which will be totally out ofcontext insofar as his motion picture is concerned. However, because theway that multiple versions of a motion picture can be stored on the samedisk in the first place is that the player can be controlled to skipover the play of certain data blocks, as will be described below, thesoftware publisher can encode his other data blocks so that the copieddata blocks are not played. In this way, the encryption protection canbe rendered ineffective.

The solution is that while the algorithm that derives the "message" M inthe first place may also operate on predetermined data blocks, it shouldoperate on at least the lead-in section of the track. There is no waythat an unauthorized publisher can copy the lead-in track fields fromanother disk because that would give a player incorrect informationabout the video and audio contents on the unauthorized publisher's disk.The lead-in data is a function of the particular subject matter of thedisk, and it must appear in the track in order for the disk to playproperly. Thus the information represented on FIG. 3 can be treated asthe "message" M whose encryptions, one for each authorized standard, arederived using respective private keys and are stored in lead-in field29. (Strictly speaking, the "message" M is the result of processing allfields except field 29. Also, the longer fields, such as thosecontaining software, can be omitted from the processing.) The playerderives the same "message", decrypts an encrypted authorization codewith the public key associated with the respective standard, and thencompares the two. If they don't match, the player determines that thatparticular standard has not been authorized for the particular disk'spublisher.

The encrypted authorization code field is shown toward the end of FIG. 3and thus the corresponding processing is depicted toward the end of theflowchart of FIGS. 5A-5C to be discussed below. The positioning of theencrypted authorization code field as shown facilitates a description ofits processing, but in fact the field may advantageously be placed atthe start of the processing. It will be recalled that special softwaremay be read from the disk to modify the normal player sequencing. It istherefore conceivable that a counterfeiter could write special softwarewhich causes the authorization code processing to be bypassed. By doingthe processing before any special software is even read, the processingcannot be bypassed.

Returning to a description of the lead-in track fields, field 30 is a1-bit data block command/data flag. This bit informs the operatingsystem whether the data blocks include command information or data whichis to be read during play of the disk. How the system determines whethera particular data block contains commands or data will be explainedbelow. Field 30 simply indicates whether there is any such informationat all. Finally, fields 31 and 32 are catch-all fields for allowing thedisk to control unusual ways in which the player processes theinformation on the disk. It will be recalled that field 3 contains aflag which indicates whether field 4 contains special software whichcauses the player to operate in accordance with a program that istotally different from that usually employed, field 12 indicates whetherfield 13 contains special mixing/deletion software for use with the"other" audio tracks, and field 17 contains a flag which indicateswhether field 18 contains special version software for processing the4-bit multiple version code. Field 31 indicates whether there is"supplemental" software in field 32. The supplemental software isdifferent from the special software of field 4 in that the software infield 4 is basically a substitute for the processing which is normallyused, while the supplemental software generally works with that code, inconjunction with commands and data which are to be found in the datablocks.

Typically, the supplemental software would allow play of a video game,with related commands and data in the data blocks determining the courseof play. But there are other uses of this technique. As another exampleof the way in which supplemental software, and commands and data in thedata blocks, can be used, consider a disk designed to play a classicmotion picture with subtitles, but which is also provided with acritical commentary which is to be displayed periodically in lieu ofsubtitles, perhaps during moments when the screen is caused to go blankexcept for the critical commentary. To show the flexibility which ispossible, let us even consider a case where the critical commentary isto be in a different language. What is required in such a case is thatthe subtitle buffer 59 on FIG. 2 be loaded during the play of some datablocks with subtitles in one language and with subtitles in anotherlanguage during play of other data blocks (some data blocks thuscontaining subtitles corresponding to the original motion picture, andothers containing critical commentary in another language). In such acase, the system must somehow be told to switch back and forth betweenlanguage subtitles, i.e., different subtitle tracks have to be processedin different data blocks. This can be conveniently controlled by issuingcommands in the data blocks themselves. Similarly, if it is desired toblank the screen and interrupt the picture during display of commentary,a data block might include a data value which represents the duration ofthe blanking. Alternatively, if a commentary is to be made in adifferent language, it could be a different audio track which isselected for the purpose. In any case, the special software loaded fromfield 32 would control the processing of the commands and data containedin the data blocks, and would work in conjunction with the operatingsystem of the player.

PROCESSING OF THE LEAD-IN TRACK FIELDS

The flowchart of FIGS. 5A-5E depicts the processing of the informationin the lead-in track fields. A description of this preliminaryprocessing is presented at this point, with the functions of theindividual fields in mind. The fields in the data blocks, as well asprocessing of the data blocks, are discussed below.

The system processing begins, as shown at the top of FIG. 5A, with thereading of default settings. These are settings established by DIPswitches, ROM codes, or the use of any other device or technique whichconfigures the system on power-up. It is typical in microprocessor-basedsystems to reset all flags and to read default settings when power isfirst turned on.

There are four default settings which are thus determined in order toconfigure the system. The first is the standard--players sold in theUnited States, for example, will typically be configured, in the defaultstate, to produce an NTSC video signal.

The next default setting is language--the sound track dialog language,the subtitle language (if any), and the language in which menus are tobe presented on the display. In the United States, for example, thedefault language would be English. If the user does not inform theplayer that a language other than English is desired for one or more ofthese functions, audio language track 10 will be used to generate thesound track, and character strings in the English language will be usedin setting up the mixing/deletion menu for the "other" audio tracks andfor the table of contents. As for subtitles, the usual default is "nolanguage."

The third default is the aspect ratio, 4:3 in the United States. Theaspect ratio determines the relative dimensions of the displayrepresented by the final video output signal.

Finally, the parental lock status is determined. In the system of FIG.2, this simply entails a determination of the setting of lock 81. But itis also possible to dispense with a physical lock and key, and to storethe parental lock status in non-volatile memory after first inputting onthe keyboard a password known only to the persons who exercise controlover the lock function.

As in many consumer electronic devices, the keyboard can be used by theuser at any time to interrogate or control the player. Routine controlsequences which are standard in the art are not shown in the flowcharts.For example, the keyboard, or an associated remote control device, canbe used to control the volume, fast forward, a jump to a specifiedchapter, etc. The normal processing can be interrupted to control adisplay by operating a menu key, as is known in the art. At the start ofthe processing of FIG. 5A, there is shown a test for determining whetherthe menu key is operated. The reason for showing an interrogation ofwhether the menu key is operated at the start of the processing, asopposed to any other time during play of the disk, is that this is themechanism by which default settings can be changed. If the menu key isoperated when power is first turned on, the system displays a menu. Asindicated in the flowchart, the user is given the choice of changingdefaults, viewing the table of contents for the disk, and/or (in casethe menu key was operated accidentally) simply returning to theprocessing without changing anything. As indicated, depending on themenu selection, the defaults are changed, the entire menu selectionprocess is aborted, or a TOC (table of contents) flag is set to 1. Thisflag will be examined later to determine whether the table of contentsshould be displayed.

Thus far, no information from the disk has been processed. (In thisdescription, references are sometimes made to reading a field andsometimes made to processing a field. It is to be understood that evenwhen it is said that after a certain processing step a field is read,the field may actually have been read earlier but stored in a buffer forlater use. Depending on the context, reading a field means to actuallyread it so that the bits appear on the DATA OUT conductor 25 in FIG. 2,or to do something with the data if it has been read earlier andbuffered.) Referring to FIG. 3, the first information field which isread from the lead-in track section is a 40-bit field representingauthorized territories. Next, a check is made to see whether theterritory in which the player was intended for use is one of thoseauthorized on the disk. The player territory is also a kind of defaultsetting, but it is not grouped with the others because it cannot bechanged by the user. (To allow a purchaser who moves from one territoryto another to use his player, the player territory can be changed by anauthorized technician.) If the player has been designed for use inChina, for example, and China is not one of the territories authorizedon the disk, play of the disk is aborted.

On the other hand, if the disk has been authorized for play in theplayer territory, field 3 is read. This single bit simply tells thesystem whether special software is present. As shown in the flowchart,if it is present then the special software is read from field 4 andexecuted. The processing terminates with the "execute special software"step. This is intended to show that the special software in field 4basically replaces the built-in operating system. Such software will beemployed when a radical change in the overall use of the player isinvolved. (As mentioned above, this is not to say that the specialsoftware may not call BIOS routines and the like from the ROM chipscontaining the operating system.)

If there is no special software present, the system reads the defaultstandard, e.g., it determines that an NTSC standard is to be employed.If the user has changed the default standard through a menu selection,e.g., to PAL, then PAL is the new default standard. The system thenaccesses field 5 which authorizes up to 12 standards. The test which isperformed is to determine whether the default standard (the original, oras changed at the start of the processing) is authorized. If it is not,a menu is displayed which shows the user the authorized standards, andhe then selects one. After an appropriate selection is made, or if thedefault standard is authorized, the system processes fields 6 and 7. Thereading of field 6 informs the player of the available audio languages(up to 16, including M&E and 15 languages).

Once again, a default value is tested against a set of allowed options.Earlier, it was the default standard that was tested against theauthorized standards read from the disk. This time it is the defaultaudio language (either the default language on power-up or a differentlanguage selected by the user if the menu key was operated) that iscompared with all of those available. As shown in the flowchart, if thedefault language is not available, a display is formed which lists theavailable audio languages, and the user selects one of them. The systemthen reads the track types in field 7. This is the field which informsthe operating system whether there is an M&E track, whether it is to beused as a mixing or a switching master, and whether the selectedlanguage track is a complete audio track, is to be mixed with the mixingmaster, or to be switched with the switching master. Next, the trackcodings are read from field 8. Given the selected language, and itstrack type and track coding, as well as information about M&E, mixingand switching, the operating system has all of the information it needsto generate a sound track for the accompanying motion picture whichmeets the needs of the viewer.

The next thing that is done is to read field 9 to determine the numberof "other" audio tracks which are on the disk, anywhere from none up to63. If there are indeed no "other" audio tracks, all of the processingto determine what is to be done with them is bypassed. But if there aresuch tracks, field 10 is first read to determine how they are coded.Since the user has to be told what is in the tracks before he candetermine what is to be done with them, the system must next determinefrom reading field 11 the "other" track menu languages which are on thedisk. The usual type of check is then made to see whether the menu isavailable in the default language. If it is not, the available languagesare displayed and the user selects one of them.

As described above, the operating system may execute a standard routinefor reading the menu, displaying it, and interacting with the user asthe user determines what should be done with the "other" audio tracks.But in the event special mixing or deletion is to be accomplished,special mixing/deletion software is required. Field 12 is read to seewhether such software is available and, as indicated in the flowchart,any special mixing/deletion software which is on the disk is read fromfield 13. Only then are the actual menu items (in the selected language)read from field 14 and displayed for the user. Using the menus madeavailable by the operating system, the user selects the play mode forthe "other" audio tracks. He can, for example, mix them in any allowedway, use what is in a track for deletion (by phase inversion) fromanother more inclusive track, adjust one track for exclusive play,adjust relative audio levels, etc. The special mixing/deletion software,of course, can provide these options as well as others not routinelyoffered.

As shown in FIG. 5B, subtitle information is now processed according tothe established pattern. First, the system determines whether subtitlesare desired at all. At the very beginning of the processing in FIG. 5A,it will be recalled that one of the default settings is the subtitlelanguage. The usual default setting will be that subtitles are notdesired. If that is in fact the case, the subtitle processing is skippedentirely. But if subtitles are desired, the available subtitle languagesare read from field 15. A test is then made to see if the defaultsubtitle language is available. If it is not, the available subtitlelanguages are displayed and the user selects one of them.

Next, the 4-bit multiple version code in field 16 is read. The first bitindicates whether there are two versions available, or only one. Abranch is not made at this point because first the system must determinewhether special version software is available, and this is determinedfrom field 17. If special version software is available, it is read fromfield 18 and executed. To the extent that this software must knowwhether multiple versions are available, and what the codes in the thirdand fourth bit positions represent, that has already been determined.Although indicated in the flowchart that the choices displayed for theuser are to select among authorized versions, or to exit, it is to beunderstood that the display choices will generally be different ifspecial version software is executed. Also, it should be understood thatthere may be special version software even if there is only one versionthat can be played. For example, it may be appropriate to warn a viewerthat a particular program may be extraordinarily unsettling, and to askfor a "continue" response before play begins--all of this being separateand apart from an R-rating.

If special version software is not available, then bits 3 and 4 in the4-bit multiple version code field are used for rating purposes. A testis performed to see whether the parental lock is on. If it is not, thenthere are no restrictions on the play of versions A and B, and bothversions are authorized. If it was previously determined that there isonly one version, then that version is considered to be version A and itis authorized.

On the other hand, if the parental lock is on, tests must be performedto see whether the versions on the disk are R-rated. As shown in FIG.5C, if version A is R-rated, and so is version B, then play of thesystem is aborted; although not shown, an appropriate message may bedisplayed to advise the user why play has stopped. If version A isR-rated but version B is not, then only version B is authorized. On theother hand, if version A is not R-rated but version B is, only version Ais authorized. Finally, even if the parental lock is on, if neitherversion is R-rated, then both versions are authorized.

The system next displays the choices available to the user. He canchoose from among the authorized versions, or he can exit and stopplaying the disk. (This latter case might arise, for example, if a childtries to watch an R-rated version, is told that it cannot be played, anda decision is made to go on to something else more interesting.)

If there is only one version available, if it is not R-rated, and ifthere is no special version software, then there may be no need for adisplay--there is only one motion picture which can be played, and thereare no restrictions on who can watch it. Nevertheless, as shown in theflowchart, the user is still given a choice between play of the disk andaborting play. The system could be designed to skip the display in sucha case and simply to assume that the user wants to watch the only motionpicture version which is on the disk. On the other hand, generating thedisplay allows the user to verify that the disk he put in the player isindeed the disk he wants.

Although the invention has been described thus far in terms of one ortwo versions of a motion picture on a disk, it is to be understood thatthere can be three or more versions. This is one of the main reasons forproviding the capability of reading special version software in thefirst place. This software can include all of the information requiredabout the several versions from which menu displays are formed so thatthe user can select what is to be played. As mentioned above, thespecial version software can allow choices between teaching and testmodes, and other options having nothing to do with whether particularmotion pictures are adult-rated.

The system next reads the video availability bit in field 11, and thusdetermines whether the data blocks which will be processed subsequentlycontain video data. If video data is present, then the base or masteraspect ratio in which it has been stored on the disk must be determined.The next step thus involves reading field 20 to ascertain whether thebase or master aspect ratio is 16:9 or 4:3. If the master aspect ratiois 4:3, the next five steps are skipped because pan scan availability isirrelevant. If the default aspect ratio is 4:3, then there is aone-to-one correspondence between stored and displayed frames; if thedefault aspect ratio is 16:9, then a 4:3 frame is displayed on a widescreen with a dark band at either side. (Alternatively, the 4:3 imagecould be expanded to fill the 16:9 screen, with resulting loss of topand/or bottom information.) But if the base aspect ratio is 16:9, asshown on FIG. 9, there are several possibilities which must be explored.

One of the default values which is determined at the very start of theprocessing is the aspect ratio. The operating system checks whether thedefault aspect ratio is pan scan 4:3. Referring to FIG. 9, if the masteraspect ratio is "wide screen" (the flowchart branch being processed),then the possibilities are letter box, pan scan centered on the widescreen image (not shown in FIG. 9), or pan scan variable (i.e., with avariable starting column number). If the default is not pan scan 4:3,then there are no choices to be made by the user now. The default iseither wide screen or letter box, and subsequent processing is inaccordance with the default which has already been determined.

On the other hand, if the default is pan scan 4:3, the issue is whethervariable pan scan information is on the disk. The pan scan availabilitybit in field 21 is read. If pan scan is available, it means that thedata blocks will specify to the operating system the starting columnnumbers for the pan scan--the user need select nothing at this point. Onthe other hand, if pan scan is not available, and this was the user'sdefault, he must decide from among two possibilities--a center cut, inwhich the middle part of every wide screen frame is displayed, or aletter box form in which the entirety of every frame can be seen, butthe display has dark bands at the top and bottom. A menu display isformed, and the user selects one of the two modes.

This use of a common aspect ratio on the disk which nevertheless allowsthe user to select from many different kinds of display exemplifies thedesign approach of the invention. The basic idea is to provide maximumflexibility while nevertheless storing all of the required data on anoptical disk roughly the size of a conventional CD. Once a wide screenmotion picture is stored on the disk, almost no additional real estateis required to allow the user to generate a video output having someother aspect ratio. Although there may be up to 15 languages in whichdialog can be heard, there are nowhere near 15 full sound tracks becauseof the mixing and switching capabilities built into the player and themanner in which redundant information is eliminated from the audiolanguage tracks. The same thing applies to video standards. While up tonow high-quality video has required a medium which can be played only inNTSC, or PAL, etc., the present invention allows the same disk to giverise to video signals in up to 12 standards. One of the advantages ofthe invention is that it greatly reduces the number of different disksthat must be produced, for example, by a motion picture company thatdistributes its movies throughout the world. While it is true that somefields may have to be changed from time to time, for example, differentstandards have to be authorized when videos are released in NTSC and inPAL at different times, such changes are relatively trivial and areeasily made.

Once a decision on the display mode is made, field 22 is read todetermine the total number of data blocks on the disk. If there aremultiple versions, fields 23 and 24 are also read in order to determinethe total number of data blocks in each of the versions. Field 25 isthen read to determine the original frame rate, and field 26 is read todetermine the block time factor.

Field 27 is then processed. It will be recalled from FIG. 3 that this isthe field that contains all of the necessary information for display ofthe table of contents. The table of contents for the selected version(field 27 if there is only one version, or there are two and the firsthas been selected; or field 28 if there are two versions and the secondhas been selected) includes a 100-bit representation of the availablechapter display languages. The default menu language is checked againstthose which are available. If the default menu language is notavailable, the user is informed of those languages in which chaptertitles can be displayed, and he selects from among them. Once it hasbeen determined in which language to display chapter information, thevarious table of contents time durations are calculated. Since it isknown how many blocks are in each chapter, the duration of each chaptercan be determined by multiplying the number of blocks by the block timefactor.

The table of contents is not necessarily displayed. It is displayed onlyif the TOC flag was set at the start of the processing, the user havingindicated that the table of contents should be displayed. If the TOCflag is 0, there is no need to display the table of contents. The systemautomatically selects the first data block as the starting point, thatis, play of the disk starts at the beginning. On the other hand, if theTOC flag is a 1, the table of contents is displayed and the user isgiven the option of selecting the start point.

Following the table or tables of contents on the disk are the encryptedauthorization codes for the standards authorized in field 5. Theoperating system reads the encrypted authorization code for the standardwhich has been selected. It then reads the predetermined data for theselected standard. It will be recalled that for each of the 12 possiblestandards, predetermined data on the disk is processed to derive a"message" M which serves as an authorization code. It is thisauthorization code that is stored in encrypted form on the disk usingthe private key associated with each standard. The data which is readfrom the disk may be different for each standard, as long as the samedata is read and processed both during the encryption process and whenthe player derives the "message" M on its own. As discussed above, it ispreferred that the data include at least part of the lead-in fieldsbecause it would be self-defeating for an authorized publisher to copythis data.

After the predetermined data for the selected standard is read, theauthorization code ("message" M) is computed from the data. Using thepublic key associated with the selected standard, which key is builtinto the operating system, the stored authorization code on the disk forthe selected standard is decrypted. The test for whether the softwarepublisher has been authorized to publish disks which will play as videosignals in the selected standard involves comparing the decryptedauthorization code with the computed authorization code. If they do notmatch, play is aborted.

If the two codes do match, field 30 is read. This single bit simplyinforms the master processor whether there are any commands or datastored in the data blocks other than the normal complement depicted inFIG. 4 to be discussed below. If the flag is a 0, the operating systemdoes not even look for such additional commands or data in the datablocks. If the flag is a 1, it means that commands or data may bepresent in a data block, but not necessarily so.

Finally, field 31 is read in order to determine whether supplementalsoftware is available. If it is, it is read from field 32. Thesupplemental software, as described above, is not to be used in lieu ofthe operating system software, but rather as a supplement to it. This isthe basic difference between the software in fields 4 and 32. Generallyspeaking, the supplemental software operates on commands and dataincluded in the data blocks in a field whose presence is indicated(although not necessarily in every data block, as will become apparentbelow) by the supplemental software flag.

With the reading of field 32 and its integration with the operatingsystem, the read head in the disk drive is caused to move to the startpoint. As described above, the start point is either the first datablock or a data block determined by the user if a chapter other than thefirst has been selected. Data blocks are read in sequence anddemultiplexer 63 on FIG. 2 distributes the data fields to variousbuffers. As indicated in the flowchart, the reading of a data blocktakes place only if no buffer is full. Furthermore, before a new datablock is read, the system checks whether there are any interrupts whichmust be serviced. Controller 41 is the source of all interrupts. Forexample, if the user has operated the keyboard, the controller generatesan interrupt on line 43 of FIG. 2 which temporarily halts the reading ofdata blocks. After the interrupt has been processed, or if there is nointerrupt which must be serviced, the next data block is read. As willbe described, the serial block number is one of the first things that isread. The block number/pointer analyzer 47 knows the number of the nextblock which is required. Very often, this will simply be the next blockin the serial sequence. However, the block number may be out ofsequence, for example, if a jump is to be made to a new chapter, or, aswill become apparent below, certain blocks have to be skipped on a diskwhen playing one of multiple versions of a motion picture. In any event,the systems checks whether the block being read is the correct one. Ifit is not, a branch is made back to the start of the block readingprocess so that a different block can be read. Also, gate 61 on FIG. 2is closed so that the "wrong" data on conductor 25 is not extended todemultiplexer 63.

If the block read is the required block, one of the first things readimmediately after the block number is pointer data. The pointer data isused by block number/pointer analyzer 47 to determine the block numberof the next data block that is required, as indicated toward the end ofthe flowchart. This block number is transmitted over cable 49 tomicroprocessor disk drive controller 27 in order that it access thisdata block at the completion of the reading of the current data block.As indicated at the end of the flowchart, the remainder of the datablock which is being processed at the moment is read and loaded into theseveral buffers, following which another data block may be read.

The flowchart just reviewed controls the processing of the player. Whatis actually done with the data read from the data blocks is shown in theflowchart of FIG. 6, and this flowchart will be described after thefields in a data block, as listed in FIG. 4, are understood. But inorder to appreciate the function of the pointer data which is includedin a data block, FIGS. 7A and 7B will be described first. These figuresdepict how data blocks associated with individual or both versions of amotion picture interrelate with each other, and how the system iscontrolled to skip over certain data blocks in order to play a selectedversion.

FIGS. 7A AND 7B--THE FUNCTION OF THE POINTER DATA

In the illustrative embodiment of the invention, there can be twoversions of the same motion picture on a disk. Most of the data blockswill represent video and audio which are common to the two versions.However, there will be other blocks that are unique to one version orthe other. The question is how to control the reading in succession ofthe data blocks that are required for a selected one of the twoversions.

For purposes of description, the letters A, B and C will be used toidentify respectively data blocks that are unique to version A of themotion picture, data blocks that are unique to version B, and datablocks that are common to both. FIG. 7B illustrates a portion of thetrack with successive data blocks being labelled A, B or C. It will beunderstood that in practice there may be thousands of data blocks insuccession of the same type, with most of the data blocks on the diskbeing of type C. However, to illustrate the way in which the systemjumps over data blocks that are not required, FIG. 7B shows at most twoblocks of the same type in succession.

There are two sequences shown in FIG. 7B, one at the top for playingversion B, and the other at the bottom for playing version A. If it isversion B that is selected, and it is assumed that somehow the B blockon the left is being played, it is apparent that the next two A blocksmust be jumped over in order to go to the fourth block, a B block. Afterthis block is played, the next A block must be jumped over. Two common Cblocks are then played, after which a jump must be made over an A blockto another C. The next block, a B, is then played, followed by B, C andB blocks. Finally, a jump is made over an A block to the last blockshown in FIG. 7B, a C block.

If version A is being played, on the other hand, two successive A blocksare played, there is then a jump over a B block, the next fiveblocks--A, C, C, A, C--are played, there is next a jump over two Bblocks to a C block, and finally there is a jump over another B block toan A and a following C.

The pattern which emerges is that there are three kinds of transitionsfrom one block to another. First, there is the play of a blockimmediately following play of the preceding block. There are sevenexamples of this shown in FIG. 7B--AA, BB, CC, CA, CB, AC and BC. Thetwo possibilities which are excluded are AB and BA, since blocks uniqueto the two versions will never be played during the same disk playing,much less one after the other. While there are seven kinds oftransitions from block type to block type, there are really just threebasic operations--going from one block of any type to the next block ofany type; a jump from either an A to an A or C, or from a B to a B or C;or a branch from a C block either to an adjacent A or B, or to a B or Asomewhere down the line. Most transitions are of the first type. Thesecond type occurs when an A is followed by a B (which two blocks cannever be played in succession); a jump must be made from the A to eitheranother A or to a C. Similar remarks apply to a B followed by an A. Thethird type occurs at the end of the play of a C block, when there is nolonger any common material to be played and a switch must be made to oneversion or the other; the next block is played if it is part of theversion selected, or some blocks will have to be jumped over if thebranch is to a block in the other version.

FIG. 7A shows the state diagram which defines how and when transitionsare made from one block to another. As will be described below, everydata block includes a two-bit pointer flag, possibly followed by a fieldwhich contains a 20-bit pointer. (When a pointer is present, it alwayspoints to the serial block number of another data block.) Referring tothe code given in FIG. 7A, if the two-bit pointer flag is 00, it is anindication that the processing should continue with the next block; inthis case, there is no need for a pointer. If the two-bit pointer flagis a 01 code, it is an indication that a jump should be made to a blockin the same version some distance away, or to a C block some distanceaway. In either case, a pointer is necessary.

The codes 10 and 11 are used when a branch is to be taken from a commonC block. Which code is used depends on whether the next block is an A orB. If the block after the C is an A, code 10 is used and the pointer isto a B or a C further down the line. If the code is 11, it means thatthe next block is a B, and the pointer is to an A or a C further alongthe track. The operating system knows which version is being played. Ifversion A is being played and the current block has a 10 pointer flag,it means that the next block, an A, should be played after the presentone. There is no need for the pointer. The pointer is necessary in caseversion B is being played. In this case, since the next block is an A,it should not be played. The player should jump to the block identifiedby the pointer--either another C, or a B unique to version B beingplayed.

Similarly, if version A is being played and the current block is a Cwith code 11 for its pointer flag, it means that the next block is a B.Since version A is being played, the next block should not be playedafter the current one. Instead, a jump is made to the A or C blockidentified by the pointer. On the other hand, if version B is beingplayed, the system simply continues to the next block.

The legend on FIG. 7A shows whether or not the pointer is used when 10and 11 pointer flags are found in a C block. The representation 10(P) isan indication that the pointer should be used, and a representation10[P] is an indication that the pointer should be ignored. It will berecalled that the 10 code is used for a C block when the next block isan A. If version A is being played, the pointer is not needed. That iswhy a transition from the C block to the succeeding block, an A, isshown by the symbol 10[P]. On the other hand, if version B is beingplayed, since the next block is an A it cannot be played after thecurrent C. Instead, there must be a jump to the block identified by thepointer and thus use of the representation 10(P)--the pointer points toeither a B block or another C.

Similar remarks apply to the representations 11(P) and 11[P]. In bothcases, it is a C block which is being played and the next block is a B.If version A is being played, the next block should not be played andthus the symbol 11(P) is required to show a state transition. On theother hand, if version B is being played, it is the succeeding B blockwhich should be played, and thus the symbol 11[P] is appropriate.

The four codes, as well as the usages (P) and [P], are depicted in FIG.7B. Referring to the PLAY B transition sequence, the first transitionshown is 01(P). It will be recalled that the 01 code represents a jumpfrom one version to a block of the same version or to a common block,and a pointer is required. The first transition shown is 01(P), a jumpfrom a B block to another B block. The next transition on the PLAY Bline is 01(P), a jump from a B to a C. Next is an example of the mostcommon transition of all, 00, the orderly play of the next block afterthe current block.

The fourth transition in the PLAY B line is represented by a 10(P)symbol. The 10 code represents a branch from a C block when the nextblock is an A, the example illustrated in FIG. 7B. In such a case, asindicated in FIG. 7A, if it is version B which is being played a jump ismade to the block identified by the pointer--in this case, the next C.

The 11 code is used to identify a branch from a C block when the nextblock is a B. If version B is being played, the case underconsideration, the pointer is not necessary because the next block is tobe played. That is why the next code shown is 11[P]. There follow two 00codes that represent obvious transitions to adjacent blocks, followed bya 11[P] code, a branch from a C block to the succeeding block which is aB. Finally, a jump is made from this B block over the next A block to aC block. This requires a 01(P) code--the code used to jump from a blockof either version to a block of the same version or a common block.

The PLAY A sequence in FIG. 7B assumes that it is version A that isbeing played. The first four codes represent transitions to adjacentblocks, or a jump from a block of one version to a block in the sameversion. The next code, 10[P], is used to show a branch from a C blockto an adjacent A block. The pointer is not used since version A is beingplayed, and code 10 is employed because the next block is an A block.The next 00 code symbolizes the transition from the A block to asucceeding C block.

Next is a jump from a C block to another C block, skipping over two Bblocks. The 11 code is used because this is the code employed when a Bblock follows a C block. The symbol used is 11(P), not 11[P], becausethe pointer is required in going from one C block to a C block furtherdown the line. Similarly, the next code is again a 11(P) code tosymbolize a branch from a C block to an A block further down the line.The sequence in FIG. 7B ends with a transition from an A block to thenext block which is a C, for which the code 00 is used.

The state diagram of FIG. 7A summarizes all possibilities. Considerfirst the state in which an A block is being processed, represented bythe circle with an A in it at the upper left. The two-bit pointer flagin an A block is 00 if the next block is also an A (shown by thetransition from A back to A). If the next block is a B, on the otherhand, then it clearly should not be played. There must be a jump fromthe A block over the B, either to another A or to a C. In either case,the code is 01(P). The drawing shows both a jump over B (to another A),and a jump over B to a C. The only other transition from an A block isto the next block if it is a C. This is shown by the code 00.

There are four similar transitions shown for state B, i.e., when a datablock in version B is being read. The 00 code is used if the next blockis a B or a C. The 01(P) code is used when the next block is an A, andit is jumped over so that the system can next read another B or a C.

Transitions from a C block are more complicated because there are sevenof them, rather than only four as for each of the A and B blocks. If thenext block is also a C, the code is a simple 00--read the next block. Ifthe next block is a B and a jump must be made to another C, the code10(P) controls the jump over the A. Similarly, the code 11(P) controls ajump over a B to another C. It will be recalled that these two codes areused to control branches from a C block, depending on whether the nextblock is an A or B. In either case, if the next block is not to be read,it (and blocks like it) must be jumped over to the next C.

However, after reading a C block, it is also possible to read an A or aB. To read an A, one of the codes 11(P) or 10[P] is used. The 11 code isemployed when the next block is a B, in which case the pointer isrequired. The 10 code is used when the next block is an A, in which casethe pointer is not used. Similarly, to read a B block next, either thecode 10(P) or 11[P] is used. The former is employed when the next blockon the disk is an A, and the pointer is required because this block mustbe jumped over. On the other hand, if the next block is a B, the code 11tells the system to go on to this next block, and in the process toignore the pointer because it is not needed.

Perhaps the most important point to recognize is one which is notapparent from the drawings, and that is that most blocks will contain 00pointer flags and no pointers. (The 00 code is the only one without afollowing pointer field.) That is because once a frame of either versionis being played, or once a frame of the common material is being played,it is most likely that the next frame will be of the same type.Consequently, a 00 code alone does the job. The net result is that twoversions of the same motion picture can be stored on the disk, with theuser having the option of playing either (provided that it is allowed bythe parental lock), and only a tiny fraction of the total disk realestate is "wasted" by housekeeping bits that control transitions fromone block to the next block which is to be read after it. Again, this isin line with the underlying design philosophy of providing maximumflexibility and as many options as possible, without unduly wasting bitsin the process.

It should also be noted that the invention is not limited to placingjust two versions of a motion picture on a disk. It is possible to usethe same technique with three or more versions (although the need for somany versions is less likely). In such a case, common blocks wouldrequire two pointers, not just one. If there are three versions on thedisk, following a C block, the next block might be an A, B or D. Twopointers would be required to point to the two blocks which are to befound further down the line. Obviously, this is just one of the changeswhich would have to be made. The point is that multiple versions can beaccommodated, albeit with an expenditure of more housekeeping bits.Nevertheless, the total number of pointer bits of this type is stillinconsequential compared with the total number of audio/video bits.

DATA BLOCK FIELDS

FIG. 4 depicts the fields of a data block, and the format is similar tothat shown for the fields of the lead-in track in FIG. 3. Every datablock begins with a sync word. As discussed above, the sync word patterncannot appear in the data, and thus when it is detected the operatingsystem knows that a new data block is about to begin.

The second field is a 20-bit serial block number. All of the blocks onthe disk are numbered in serial order. The block number is the firstthing read because it is used by block number/pointer analyzer 47 inFIG. 2. The block number is essential, for example, when jumping fromone block to another. The read head will usually be positioned at apoint near the desired block, but it is highly unlikely that the correctblock will be selected on the first try. This is especially true sincethe number of bits in the data blocks is variable, and the system has noway of knowing how many bits there are in the blocks being skipped. Byreading the block number at the start of the data block, the system canquickly determine whether the head must be repositioned.

The third field is a two-bit code which represents whether the block ispart of the A version, the B version, or common to both. (Only three ofthe four possible codes are used.) It might be wondered why the systemwould ever have to check on the version of a particular block, sinceonce play of version A or version B begins, the pointers discussed inconnection with FIGS. 7A and 7B will always identify a block which iseither common or part of the version being played. The answer has to dowith fast forward and fast reverse operations. Although these have notbeen discussed at length because they are entirely conventionaltechniques, when fast forwarding, for example, the read head may bepositioned more or less arbitrarily. The video should not be shown if itis of the wrong version. It is not possible to determine the version ofa block simply by looking at the block number or the pointer. Neitheridentify the version. It is for this reason that the system must be ableto determine the version of the block when it is first read.

Fields 4 and 5 contain the two-bit pointer flag and 20-bit pointer whichhave been explained at length in connection with FIGS. 7A and 7B.

Field 6 is a one-bit flag which may or may not be present. Referring toFIG. 3, the video availability flag in field 19 tells the operatingsystem whether there is any video in the data blocks. Even if there is,however, it does not mean that every data block contains video. For asystem in which there is a single frame represented in every data block,and data blocks are processed at a fixed rate, there would be video inevery data block, even if it is "minimal" video which consists of a coderepresenting a "no change." But there may be systems in which a datablock may represent more or less than a single frame. For example, itmay be that the video information in a data block, if present at all, isalways of the same number of bits. Depending upon the compression, itmay be that many frames are represented in a single data block. In sucha case, some of the blocks would be devoid of video bits. Depending uponthe coding scheme employed, the bit in field 6 informs the operatingsystem whether there is a field 7 at all. If there is video, field 7contains the video information, terminating with a sync word. Asmentioned above, the actual coding of the video and audio blocks doesnot comprise part of the subject invention. Although MPEG schemes arepreferred, others can be used.

Field 8 contains anywhere from no bits up to 16. It will be recalledthat field 6 of the lead-in track contains 100 bit positions, but only Nof these (where the maximum N is 16) can represent bits of value 1because there can be at most 16 audio tracks on the disk (of which M&Eis considered to be one of them). For each of these N tracks, field 8informs the operating system whether there is any audio in the presentdata block. There are thus X "1"s, up to a maximum of N. The first bitposition of N-bit field 8 corresponds with the first audio languagetrack identified in field 6 of the lead-in track. The second bit infield 8 of a data block is associated with the second audio languagerepresented in field 6 of the lead-in track, etc. The reason that thereare only N (maximum=16) bits in field 8 of FIG. 4, rather than 100, isthat it is known from the lead-in track which are the languages that maybe present in a data block. There is no reason to provide 84 or more bitpositions in each data block to indicate that the correspondinglanguages are not present when it is known from the lead-in track thatthey are nowhere to be found on the disk. It must be borne in mind thatthe value X in FIG. 4 does not equal the value N in FIG. 3. The latterrepresents the total number of audio languages anywhere on the disk, andits maximum value is 16. The symbol X represents how many of those N areactually represented in the current data block.

Field 9 contains the X audio language blocks. Suppose that there are 10audio languages represented on the disk, but only six of them arerepresented in the current data block. In this case, there would be Xbit sequences corresponding to the audio languages, each ending with anescape character. The escape character is used to separate audio blocksfrom each other. If whenever an audio block is present it has a fixedduration, then, since it is known how many audio blocks are present in adata block from the information in field 8, it is not necessary toprovide a sync word at the end of the field. Variable length audioblocks would require a sync word at the end of the field.

Field 9 in the lead-in track contains a value from 0 to 63 whichrepresents the number of "other" audio tracks. While there may be M such"other" audio tracks, as shown in FIG. 3, it does not mean that each ofthem is represented in the current data block. Field 10 in each datablock contains M bits, one for each of the "other" audio tracks on thedisk. Whether the current data block actually contains bit informationfor any of these M tracks depends on whether the corresponding bitposition in field 10 contains a 1. If there are Y "1"s and Y is lessthan M, it means that not all of the "other" audio tracks arerepresented in the current data block. Field 11 contains Y "other" audiotrack blocks, each ending with an escape character. It will beappreciated that the way the audio tracks and the "other" audio tracksare represented in the data block are comparable.

Referring back to FIG. 2, it will be recalled that data bits in a datablock are distributed to audio buffers, a video buffer, a pan scanbuffer and a subtitle buffer, as well as to master controller 41 overthe COMMAND/DATA line 65. Thus far, the representation of audio blocks,"other" audio blocks and a video block have been considered in theanalysis of the fields of FIG. 4. Before proceeding with therepresentation of the subtitle data, however, it must be understood thatthere is a difference in the way that subtitle information isrepresented, as opposed to all audio and video data. The latter isrepresented on a block-by-block basis, and the buffers are continuouslyreplenished with new audio and video data. Subtitles, on the other hand,need not change from frame to frame. In fact, a subtitle will not evenbe perceived if it does not remain on the screen for more than oneframe. Consequently, once subtitle data is represented in buffer 59 ifFIG. 2, it causes a subtitle to be formed on the display and to remainthere until new subtitle information is loaded into the buffer. Toremove a subtitle without introducing a new one, a new subtitleconsisting of a blank field is loaded into the buffer.

Field 12 in the data block consists of P bits, each corresponding with adifferent one of the P subtitle languages identified in field 15 of thelead-in track. (It will be recalled that the first position in every100-bit field corresponding to languages does not really represent alanguage, but rather M&E, so that there are a maximum of 99 subtitlelanguages.) Any subtitle for which there is an update in the currentdata block has a 1 in its corresponding position in field 12. There canbe up to Z "1"s, where the maximum value of Z is P.

For each subtitle language for which there is an update in the currentdata block, the update appears in field 13. There are Z update blocks,each ending with an escape character. It is important to understand thatan update block can be a blank field. This is the way in which asubtitle is removed when a new subtitle is not yet to take its place.

Field 14 consists of one bit which may or may not be present. The fieldis present only if field 21 in the lead-in track is a 1. In such a case,pan scan information is available in the data blocks. If pan scaninformation is available, each data block must tell the operating systemwhether it actually contains a new starting column for the pan scan.Field 14 is a single bit, a flag, which indicates whether there is a panscan update. If the bit is a 1, field 15 is a 9-bit column number, i.e.,a pan scan update.

Finally, field 16 is a single bit which may or may not be present,depending on the value of field 30 in the lead-in track. This one-bitflag in the lead-in track tells the operating system whethersupplemental commands and data may be present in field 17 of a datablock. If the command/data present flag is a 1, the command/data blockis read from field 17. The field ends with an escape character.

A data block field thus contains up to six different types ofdata--audio, "other" audio, video, pan scan information, subtitles and acommand/data block. These are the six types of information which werediscussed above in connection with FIG. 2, with demultiplexer 63distributing the different blocks of information to the audio buffers,video buffer, pan scan buffer, subtitle buffer and master controller.

PROCESSING OF THE DATA BLOCK FIELDS

The processing of the data in a data block is relativelystraightforward. The processing shown in the flowchart of FIG. 6dovetails with the data block fields themselves shown in FIG. 4.

It has already been described how block number/pointer analyzer 47 onFIG. 2 processes the serial block number, version, two-bit pointer flagand pointer contained in fields 2-5 of a data block. The next field isthe video present flag. As shown on FIG. 6, if it is determined thatvideo data is present, video buffer 55 on FIG. 2 is loaded with thevideo in field 7. If video data is not present, the buffer simply has amarker loaded into it.

It is important to understand the need for markers. In order for theoperating system always to be able to synchronize video, audio,subtitle, etc. information, it must be able to tell where in the severaldifferent buffers is the information from the same data block. In otherwords, the operating system must know which part of the audio data in anaudio buffer goes with which part of video data in the video buffer.Otherwise the various information items cannot be synchronized with eachother. By providing markers in the buffers for data which is not presentin the data blocks, the operating system can keep the various items ofinformation synchronized with each other.

Next, the operating system looks at field 8 to determine how many of theN audio tracks on the disk (see FIG. 3) actually are represented in thecurrent data block. The same is true of the M "other" audio tracksrepresented in field 10. All of the audio and "other" audio track dataare loaded into their respective buffers. The flowchart shows thesequencing only for the first and last of the audio tracks. In eachcase, a test is performed to see whether the audio track or "other"audio track has data present in the current data block. Each of thetracks results in something being loaded in its respectivebuffer--either actual data followed by a marker, or a marker alone.

After the video and audio information, a data block contains subtitleupdates. If there is update information for the subtitles in theselected language, it is loaded in the subtitle buffer; otherwise amarker alone is stored. The three blocks pertaining to subtitles pertainonly to a single track, that corresponding to the selected subtitlelanguage.

Next, the pan scan update flag in field 14 is read. If pan scan updateinformation is present, it also gets loaded, this time in a pan scanbuffer. If no new information is available, a marker is simply placed inthe pan scan buffer to indicate that another data block has gone by withno new pan scan update information.

Finally, the system determines whether there are commands or dataavailable (if the lead-in track field 30 says that commands or data areto be found at all in the data blocks). If command/data is present,i.e., field 16 in the data block is a 1, it is loaded from field 17 intomemory in the master controller 41 of FIG. 2. If there are no commandsor data available only a marker is loaded in the microprocessor memory.

It should be noted that none of the processing sequences of FIG. 6 showsa check being made whether the respective type of information isavailable on the disk in the first place. But it is to be understoodthat a test such as "is command/data present?" really consists of twoparts. First, is the data block command/data flag in field 30 of thelead-in track a 0 or 1? If it is a 0, commands and data are not evenlooked for during the processing of a data block. On the other hand, ifcommand or data may be present in a data block as a result of the dataflag in field 30 of the lead-in track being a 1, then each data blockhas its field 16 checked to see whether the command/data present flag isa 1. It is the value of the flag in the data block field whichdetermines whether only a marker gets loaded, or a marker following databits. Similar remarks apply to the other sequences. For example, thereis no reason to check whether a pan scan update is present if from thelead-in track it is determined that pan scan information is nowherepresent on the disk.

Although the invention has been described with reference to a particularembodiment, it is to be understood that this embodiment is merelyillustrative of the application of the principles of the invention.Numerous modifications may be made therein and other arrangements may bedevised without departing from the spirit and scope of the invention.

We claim:
 1. An optical disk for use in a compatible player forrepresenting a plurality of signals which are to be played synchronizedwith each other, said signals being represented on the disk in the formof digital data, with each of said signals being represented by a bitstream designed to be processed during play of the optical disk at arate which varies with the information content of the signal itself andwith the bit rates for said plurality of signals being independent ofeach other, the digital data on the optical disk being organized in aseries of data blocks with the data blocks containing variable numbersof bits of each bit stream, the bit streams being distributed among thedata blocks such that bits of each bit stream, after being read from thedisk and buffered by a compatible player, are at all times available asrequired for proper reconstruction of the respective represented signal.2. An optical disk in accordance with claim 1 wherein some data blockshave no bits of one or more of said bit streams.
 3. An optical disk inaccordance with claim 2 wherein each of said data blocks contains codesindicative of which bit streams have bits contained in such data block.4. An optical disk in accordance with claim 3 wherein each of said datablocks contains characters identifying the boundaries of the differentbit streams contained therein.
 5. An optical disk in accordance withclaim 3 wherein a lead-in section of the optical disk contains codesidentifying the individual bit streams contained in said series of datablocks.
 6. An optical disk in accordance with claim 1 wherein each ofsaid data blocks contains codes indicative of which bit streams havebits contained in such data block.
 7. An optical disk in accordance withclaim 6 wherein each of said data blocks contains characters identifyingthe boundaries of the different bit streams contained therein.
 8. Anoptical disk in accordance with claim 7 wherein a lead-in section of theoptical disk contains codes identifying the individual bit streamscontained in said series of data blocks.
 9. An optical disk inaccordance with claim 1 wherein each of said data blocks containscharacters identifying the boundaries of the different bit streamscontained therein.
 10. An optical disk in accordance with claim 9wherein a lead-in section of the optical disk contains codes identifyingthe individual bit streams contained in said series of data blocks. 11.An optical disk in accordance with claim 1 wherein a lead-in section ofthe optical disk contains codes identifying the individual bit streamscontained in said series of data blocks.
 12. A system for playing anoptical disk, said disk representing a plurality of signals which are tobe played synchronized with each other, said signals being representedon the disk in the form of digital data, with each of said signals beingrepresented by a bit stream designed to be processed during play of theoptical disk at a rate which varies with the information content of thesignal itself and with the bit rates for said plurality of signals beingindependent of each other, the digital data on the optical disk beingorganized in a series of data blocks with the data blocks containingvariable numbers of bits of each bit stream; said system comprisingbuffer means for each of said bit streams, means for reading the datablocks on an optical disk and for distributing the bits of each bitstream contained therein to a respective buffer means, and means foraccessing the bits in each of said buffer means and for generating therespective signal represented thereby.
 13. A system in accordance withclaim 12 further including means for inhibiting reading of further datablocks when any of said buffer means is full.
 14. A system in accordancewith claim 12 wherein each of said data blocks contains codes indicativeof which bit streams have bits contained in such data block andcharacters identifying the boundaries of the different bit streamscontained therein, and said reading and distributing means operates inaccordance with said data block codes and characters.
 15. A system inaccordance with claim 14 wherein said buffer means are long enough andsaid bit streams are distributed among the data blocks such that eachbuffer contains a sufficient number of bits to satisfy the immediateneeds of the accessing means for the respective signal.
 16. A system inaccordance with claim 12 wherein said buffer means are long enough andsaid bit streams are distributed among the data blocks such that eachbuffer contains a sufficient number of bits to satisfy the immediateneeds of the accessing means for the respective signal.
 17. A method forplaying an optical disk, said optical disk representing a plurality ofsignals which are to be played synchronized with each other, saidsignals being represented on the disk in the form of digital data, witheach of said signals being represented by a bit stream designed to beprocessed during play of the optical disk at a rate which varies withthe information content of the signal itself and with the bit rates forsaid plurality of signals being independent of each other, the digitaldata on the optical disk being organized in a series of data blocks withthe data blocks containing variable numbers of bits of each bit stream;said method comprising the steps of reading the data blocks on anoptical disk and buffering the individual bit streams contained therein,and accessing the individually buffered bit streams and generating therespective signals represented thereby.
 18. A method in accordance withclaim 17 further including the step of inhibiting reading of furtherdata blocks when the buffering capacity for any bit stream is fullyutilized.
 19. A method in accordance with claim 17 wherein each of saiddata blocks contains codes indicative of which bit streams have bitscontained in such data block and characters identifying the boundariesof the different bit streams contained therein, and said reading andbuffering steps are carried out in accordance with said data block codesand characters.
 20. A method in accordance with claim 19 wherein saidbuffering capacities are large enough and said bit streams aredistributed among the data blocks such that there are always available asufficient number of bits to satisfy the immediate bit accessing needsof all signals.
 21. A method in accordance with claim 17 wherein saidbuffering capacities are large enough and said bit streams aredistributed among the data blocks such that there are always available asufficient number of bits to satisfy the immediate bit accessing needsof all signals.